Polyamide compound

ABSTRACT

A polyamide compound containing from 0.1 to 50 mol % of a diamine unit that contains at least 50 mol % of a linear aliphatic diamine unit represented by the following general formula (I), from 0.1 to 50 mol % of a dicarboxylic acid unit that contains a linear aliphatic dicarboxylic acid unit represented by the following general formula (II-1) and/or an aromatic dicarboxylic acid unit represented by the following general formula (II-2) in an amount of at least 50 mol % in total, and from 0.1 to 50 mol % of a constituent unit represented by the following general formula (III): 
                         
[In the above-mentioned general formulae (I) and (II-1), m and n each independently indicate an integer of from 2 to 18. In the general formula (II-2), Ar represents an arylene group. In the general formula (III), R represents a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.]

TECHNICAL FIELD

The present invention relates to a polyamide compound (includingpolyamide resin and polyamide oligomer) capable of expressing oxygenabsorption performance, and to a polyamide composition containing thepolyamide compound.

BACKGROUND ART

Heretofore, metal cans, glass bottles, or containers or molded productsof thermoplastic resin and the like are used as packaging materials fordrugs, drinks, foods, chemicals, etc. Above all, containers and moldedproducts of thermoplastic resin excel any others in theirlightweightness, formability, packages producibility such assealability, and cost, and are used most popularly. However, in general,containers and molded products of thermoplastic resin are excellent aspackaging materials but have some problems in point of their storabilityfor the contents therein since oxygen penetration through the containerwall thereof occurs on a non-negligible order level.

For preventing oxygen penetration from the outside thereof, thecontainers and the molded products of thermoplastic resin are so plannedthat the container wall could have a multilayer structure, at least onelayer of which is an oxygen barrier layer of polymetaxylylenadipamide(hereinafter referred to as “N-MXD6”), ethylene/vinyl alcohol copolymer,polyacrylonitrile, aluminium foil or the like. However, it is stillimpossible to fully prevent even slight oxygen from penetrating into thecontainers from outside, and is also impossible to prevent the contentssensible to oxygen such as beer or the like from being deteriorated byoxygen remaining in the containers.

For removing oxygen from containers, an oxygen absorbent has been usedin the past. For example, Patent References 1 and 2 describe anoxygen-absorbing multilayer structure and an oxygen-absorbing film withan oxygen absorbent such as iron powder or the like dispersed in resin.Patent Reference 3 describes an oxygen-collecting barrier for packagingcapable of absorbing oxygen inside and outside a container formed of apolymer material such as polyamide or the like with a metallic catalystsuch as cobalt or the like added thereto. Patent Reference 4 describes aproduct having an oxygen-scavenging layer that contains an ethylenicunsaturated compound such as polybutadiene or the like and a transitionmetal catalyst such as cobalt or the like, and an oxygen-blocking layerof polyamide or the like.

CITATION LIST Patent References

-   Patent Reference 1: JP-A 2-72851-   Patent Reference 2: JP-A 4-90848-   Patent Reference 3: Japanese Patent 2991437-   Patent Reference 4: JP-A 5-115776

SUMMARY OF THE INVENTION Problems that the Invention is to Solve

The oxygen-absorbing multilayer structure and the oxygen-absorbing filmwith an oxygen absorbent such as iron powder or the like dispersed inresin are nontransparent since the resin is colored with the oxygenabsorbent such as iron powder or the like therein, and are thereforeconstrained in point of the use thereof in that they could not be usedin the field of packaging that requires transparency.

On the other hand, the oxygen-trapping resin composition that contains atransition metal such as cobalt or the like is advantageous in that itis applicable also to packaging containers that require transparency,but is unfavorable since the resin composition is colored by thetransition metal catalyst. In addition, in the resin composition, theresin absorbs oxygen and is thereby oxidized in the presence of thetransition metal catalyst. Concretely, it is considered that oxygenabsorption would be caused by various reactions of radical generation tobe caused by the transition metal atom to draw away the hydrogen atomaway from the methylene chain adjacent to the arylene group in thepolyamide resin, peroxy radical generation to be caused by oxygenmolecule addition to the radical, hydrogen atom drawing to be caused bythe peroxy radical and the like. Since the resin is oxidized through theoxygen absorption of the mechanism as above, there occur variousproblems in that a decomposed product is generated to give anunfavorable odor to the contents in the containers, and the resin isdeteriorated through oxidation to thereby discolor the containers orlower the strength of the containers.

An object of the present invention is to provide a polyamide compoundand a polyamide composition, which can express sufficient oxygenabsorption performance even though not containing a metal, which do notgenerate any offensive odor and which have an extremely goodtransparency.

Means for Solving the Problems

The present invention provides a polyamide compound and a polyamidecomposition mentioned below.

<1> A polyamide compound containing from 0.1 to 50 mol % of a diamineunit that contains at least 50 mol % of a linear aliphatic diamine unitrepresented by the following general formula (I), from 0.1 to 50 mol ofa dicarboxylic acid unit that contains a linear aliphatic dicarboxylicacid unit represented by the following general formula (II-1) and/or anaromatic dicarboxylic acid unit represented by the following generalformula (II-2) in an amount of at least 50 mol % in total, and from 0.1to 50 mol % of a constituent unit represented by the following generalformula (III):

[In the above-mentioned general formulae (I) and (II-1), m and n eachindependently indicate an integer of from 2 to 18. In the generalformula (II-2), Ar represents an arylene group. In the general formula(III), R represents a substituted or unsubstituted alkyl group, or asubstituted or unsubstituted aryl group.]<2> A Polyamide Composition Containing the Polyamide Compound of theAbove <1>.

Advantage of the Invention

The polyamide compound and the polyamide composition of the presentinvention are excellent in oxygen absorption performance. Accordingly,for example, the polyamide compound and the polyamide composition of thepresent invention are favorable for use as an oxygen absorbent, ascapable of being filled in pouches or the like. A more preferredembodiment of using the polyamide compound and the polyamide compositionof the present invention is using them in packaging materials andpackaging containers. The packaging materials and packaging containersusing the polyamide compound or the polyamide composition of the presentinvention can express sufficient oxygen absorption performance eventhough not containing a metal, do not generate any offensive odor, canhave an extremely good transparency and can store the contents thereinin a good condition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 This is a ¹H-NMR chart of the polyamide compound produced inExample 1.

FIG. 2 This is a partly enlarged view of FIG. 1.

FIG. 3 This is a ¹H-NMR chart of the polyamide compound produced inComparative Example 1.

MODE FOR CARRYING OUT THE INVENTION 1. Polyamide Compound

The polyamide compound of the present invention contains from 0.1 to 50mol % of a diamine unit that contains at least 50 mol % of a linearaliphatic diamine unit represented by the following general formula (I),from 0.1 to 50 mol % of a dicarboxylic acid unit that contains a linearaliphatic dicarboxylic acid unit represented by the following generalformula (II-1) and/or an aromatic dicarboxylic acid unit represented bythe following general formula (II-2) in an amount of at least 50 mol %in total, and from 0.1 to 50 mol % of a tertiary hydrogen-containingcarboxylic acid unit (preferably a constituent unit represented by thefollowing general formula (III)):

[In the above-mentioned general formulae (I) and (II-1), m and n eachindependently indicate an integer of from 2 to 18. In the generalformula (II-2), Ar represents an arylene group. In the general formula(III), R represents a substituted or unsubstituted alkyl group, or asubstituted or unsubstituted aryl group.]

However, the total of the diamine unit, the dicarboxylic acid unit andthe tertiary hydrogen-containing carboxylic acid unit should not exceed100 mol %. The polyamide compound of the present invention may containany other constituent unit than the above-mentioned within a range notdetracting from the advantage of the present invention.

The polyamide compound of the present invention includes a polyamideresin and a polyamide oligomer.

The “polyamide resin” of the present invention means a polymer having arelative viscosity of at least 1.5 of the polyamide compound of thepresent invention. The polyamide resin is a material capable of beingworked and formed by itself, and can be worked and formed into packagingmaterials and packaging containers. If desired, any other resin andadditive may be added to and mixed in the polyamide resin of the presentinvention, and the polyamide composition thus obtained can be worked andformed. The polyamide resin of the present invention can expresssufficient oxygen absorption performance even though not containing ametal, and does not generate any offensive odor, and can have anextremely good transparency.

The “polyamide oligomer” of the present invention means a polymer havinga relative viscosity of less than 1.5 of the polyamide compound of thepresent invention. The polyamide oligomer is a material that cannot begenerally worked and formed by itself. In many cases in general, anoligomer indicates a polymer having a number-average molecular weight ofat most 1000, but the polyamide oligomer of the present inventionincludes not only such an ordinary oligomer but also a polymer having anumber-average molecular weight of less than 10000.

The polyamide oligomer of the present invention is favorable for use asan oxygen absorbent, as capable of being filled in pouches or the like.In addition, the polyamide oligomer of the present invention isfavorably used as a resin material or a resin additive. In case wherethe polyamide oligomer of the present invention is used as a resinmaterial, the polyamide oligomer may be copolymerized with any otherresin material to give a copolymer resin, and the copolymer resin may beworked and formed into packaging materials or packaging containers. Incase where the polyamide oligomer of the present invention is used as aresin additive, the polyamide oligomer may be added to a resin to give apolyamide composition, which may be worked and formed into packagingmaterials or packaging containers. In this case, the polyamide oligomercan express sufficient oxygen absorption performance withoutdeterioration of the transparency and the mechanical strength of theresin. The copolymer resin or the polyamide composition obtained by theuse of the polyamide oligomer of the present invention can expresssufficient oxygen absorption performance even though not containing ametal, and does not generate any offensive odor.

In the polyamide compound of the present invention, the content of thetertiary hydrogen-containing carboxylic acid unit is from 0.1 to 50 mol%. When the content of the tertiary hydrogen-containing carboxylic acidunit is less than 0.1 mol %, then the compound could not expresssufficient oxygen absorption performance. On the other hand, when thecontent of the tertiary hydrogen-containing carboxylic acid unit is morethan 50 mol %, then the tertiary hydrogen content is too high, and ifso, the physical properties such as the gas barrier property and themechanical properties of the polyamide compound may worsen; and inparticular, when the tertiary hydrogen-containing carboxylic acid is anamino acid, then not only the heat resistance of the compound is poorsince peptide bonds continue therein but also a cyclic product of adimer of the amino acid is formed to interfere with polymerization. Fromthe viewpoint of the oxygen absorption performance and other propertiesof the polyamide compound, the content of the tertiaryhydrogen-containing carboxylic acid unit is preferably at least 0.2 mol%, more preferably at least 1 mol %, and is preferably at most 40 mol %,more preferably at most 30 mol %.

In the polyamide compound of the present invention, the diamine unitcontent is from 0.1 to 50 mol %, and from the viewpoint of the gasbarrier performance, the oxygen absorption performance and the polymerproperties of the compound, the content is preferably from 10 to 50 mol%. Similarly, in the polyamide compound of the present invention, thedicarboxylic acid unit content is from 0.1 to 50 mol %, preferably from10 to 50 mol %.

Regarding the ratio of the diamine unit content to the dicarboxylic acidunit content, preferably, the two are nearly in the same amount from theviewpoint of the polymerization reaction thereof. More preferably, thedicarboxylic acid unit content is ±2 mol % of the diamine unit content.When the dicarboxylic acid unit content exceeds the range of ±2 mol % ofthe diamine unit content, then the degree of polymerization of thepolyamide compound could hardly increase and therefore more time isneeded for increasing the degree of polymerization thereof, thereforeoften causing thermal degradation of the compound.

1-1. Diamine Unit

The diamine unit in the polyamide compound of the present inventioncontains the linear aliphatic diamine unit represented by theabove-mentioned general formula (I) in an amount of at least 50 mol % ofthe diamine unit, from the viewpoint of increasing the degree ofpolymerization of the compound and of giving suitable crystallinity tothe compound; and the content is preferably at least 70 mol %, morepreferably at least 80 mol %, even more preferably at least 90 mol %,but is preferably at most 100 mol %.

In the general formula (I), m indicates an integer of from 2 to 18,preferably from 3 to 16, more preferably from 4 to 14, even morepreferably from 6 to 12. The compound capable of constituting the linearaliphatic diamine unit represented by the above-mentioned generalformula (I) includes aliphatic diamines such as ethylenediamine,N-methylethylenediamine, 1,3-propylenediamine, tetramethylenediamine,pentamethylenediamine, hexamethylenediamine, heptamethylenediamine,octamethylenediamine, nonamethylenediamine, decamethylenediamine,undecamethylenediamine, dodecamethylenediamine, etc., to which, however,the present invention is not limited. One alone or two or more of thesemay be used here either singly or as combined.

The linear aliphatic diamine unit in the polyamide compound of thepresent invention preferably contains a hexamethylenediamine unit in anamount of at least 50 mol % from the viewpoint of the reactivity inpolymerization and of the crystallinity and the workability of thepolyamide compound, more preferably at least 70 mol %, even morepreferably at least 80 mol %, still more preferably at least 90 mol %,but preferably at most 100 mol %.

The compound capable of constituting any other diamine unit than thealiphatic diamine unit represented by the general formula (I) includesaromatic diamines such as orthoxylylenediamine, metaxylylenediamine,paraxylylenediamine, paraphenylenediamine, etc.; alicyclic diamines suchas 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane,etc., to which, however, the present invention is not limited.

1-2. Dicarboxylic Acid Unit

The dicarboxylic acid unit in the polyamide compound of the presentinvention contains the linear aliphatic dicarboxylic acid unitrepresented by the above-mentioned general formula (II-1) and/or thearomatic dicarboxylic acid unit represented by the general formula(II-2) in an amount of at least 50 mol % in total in the dicarboxylicacid unit, from the viewpoint of the reactivity in polymerization andthe crystallinity and the formability of the polyamide compound; and thecontent is preferably at least 70 mol %, more preferably at least 80 mol%, even more preferably at least 90 mol %, but is preferably at most 100mol %.

The compound capable of constituting the other dicarboxylic acid unitthan the dicarboxylic acid unit represented by the general formula(II-1) or (II-2) includes dicarboxylic acids such as oxalic acid,malonic acid, fumaric acid, maleic acid, 1,3-benzene-diacetic acid,1,4-benzene-diacetic acid, etc., to which, however, the presentinvention is not limited.

In the dicarboxylic acid unit in the polyamide compound of the presentinvention, the content ratio of the linear aliphatic dicarboxylic acidunit to the aromatic dicarboxylic acid unit (linear aliphaticdicarboxylic acid unit/aromatic dicarboxylic acid unit) is notspecifically restricted, and may be suitably determined depending on theintended use. For example, in case where the glass transitiontemperature of the polyamide compound is desired to be elevated and thecrystallinity of the polyamide compound is thereby desired to belowered, the ratio of linear aliphatic dicarboxylic acid unit/aromaticdicarboxylic acid unit is preferably from 0/100 to 60/40 relative to thetotal of the two, 100, and is more preferably from 0/100 to 40/60, evenmore preferably from 0/100 to 30/70. In case where the glass transitiontemperature of the polyamide compound is desired to be lowered and thepolyamide compound is thereby desired to be more flexible, then theratio of linear aliphatic dicarboxylic acid unit/aromatic dicarboxylicacid unit is preferably from 40/60 to 100/0 relative to the total of thetwo, 100, and is more preferably from 60/40 to 100/0, even morepreferably from 70/30 to 100/0.

1-2-1. Linear Aliphatic Dicarboxylic Acid Unit

In case where the polyamide compound of the present invention is desiredto have a suitable glass transition temperature and suitablecrystallinity, and in addition thereto, the compound is further desiredto have suitable flexibility necessary for packaging materials andpackaging containers, then the compound preferably contains the linearaliphatic dicarboxylic acid unit represented by the above-mentionedgeneral formula (II-1).

In the general formula (II-1), n indicates an integer of from 2 to 18,preferably from 3 to 16, more preferably from 4 to 12, even morepreferably from 4 to 8.

The compound capable of constituting the linear aliphatic dicarboxylicacid unit represented by the general formula (II-1) includes succinicacid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaicacid, sebacic acid, 1,10-decanedicarboxylic acid,1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, etc., towhich, however, the present invention is not limited. One alone or twoor more of these may be used here either singly or as combined.

The type of the linear aliphatic dicarboxylic acid unit represented bythe general formula (II-1) can be suitably determined depending on theintended use thereof. The linear aliphatic dicarboxylic acid unit in thepolyamide compound of the present invention preferably contains at leastone selected from a group consisting of an adipic acid unit, a sebacicacid unit and a 1,12-dodecanedicarboxylic acid unit in an amount of atleast 50 mol % in total in the linear aliphatic dicarboxylic acid unit,from the viewpoint of giving an excellent gas barrier property to thepolyamide compound and, in addition thereto, from the viewpoint that thepackaging materials and the packaging containers using the polyamidecompound can still keep heat resistance after thermal sterilizationthereof; and the content is more preferably at least 70 mol %, even morepreferably at least 80 mol %, still more preferably at least 90 mol %,but is preferably at most 100 mol %.

The linear aliphatic dicarboxylic acid unit in the polyamide compound ofthe present invention preferably contains an adipic acid unit in anamount of at least 50 mol % in the linear aliphatic dicarboxylic acidunit from the viewpoint of the gas barrier property of the polyamidecompound and of thermal properties such as suitable glass transitiontemperature or melting point thereof. The linear aliphatic dicarboxylicacid unit in the polyamide compound of the present invention preferablycontains a sebacic acid unit in an amount of at least 50 mol % in thelinear aliphatic dicarboxylic acid unit from the viewpoint of givingsuitable gas barrier property and forming workability to the polyamidecompound; and in case where the polyamide compound is used for thosethat are required to have low water absorbability, weatherability andheat resistance, the linear aliphatic dicarboxylic acid unit preferablycontains a 1,12-dodecanedicarboxylic acid unit in an amount of at least50 mol % therein.

1-2-2. Aromatic Dicarboxylic Acid Unit

The polyamide compound of the present invention preferably contains thearomatic dicarboxylic acid unit represented by the above-mentionedgeneral formula (II-2) in order that the polyamide compound is given abetter gas barrier property and, in addition thereto, in order that thecompound could easily be worked and formed into packaging materials andpackaging containers.

In the general formula (II-2), Ar represents an arylene group. Thearylene group is preferably an arylene group having from 6 to 30 carbonatoms, more preferably from 6 to 15 carbon atoms, including, forexample, a phenylene group, naphthylene group, etc.

The compound capable of constituting the aromatic dicarboxylic acid unitrepresented by the general formula (II-2) includes terephthalic acid,isophthalic acid, 2,6-naphthalenedicarboxylic acid, etc., to which,however, the present invention is not limited. One alone or two or moreof these can be used here either singly or as combined.

The type of the aromatic dicarboxylic acid unit represented by thegeneral formula (II-2) can be suitably determined depending on theintended use thereof. The aromatic dicarboxylic acid unit in thepolyamide compound of the present invention preferably contains at leastone selected from a group consisting of an isophthalic acid unit, aterephthalic acid unit and a 2,6-naphthalenedicarboxylic acid unit in anamount of at least 50 mol % in total in the aromatic dicarboxylic acidunit; and the content is more preferably at least 70 mol %, even morepreferably at least 80 mol %, still more preferably at least 90 mol %,but is preferably at most 100 mol %. Of those, isophthalic acid and/orterephthalic acid are more preferably contained in the aromaticdicarboxylic acid unit. The content ratio of the isophthalic acid unitto the terephthalic acid unit (isophthalic acid unit/terephthalic acidunit) is not specifically defined, and may be suitably determineddepending on the intended use. For example, from the viewpoint ofsuitably lowering the glass transition temperature and thecrystallinity, the ratio is preferably from 0/100 to 100/0 relative tothe total of the two units, 100, more preferably from 0/100 to 60/40,even more preferably from 0/100 to 40/60, still more preferably from0/100 to 30/70.

1-3. Tertiary Hydrogen-Containing Carboxylic Acid Unit

The tertiary hydrogen-containing carboxylic acid unit in the presentinvention has at least one amino group and at least one carboxyl groupor has at least two carboxyl groups from the viewpoint of polymerizationfor the polyamide compound. As specific examples, there are mentionedconstituent units represented by any of the following general formula(III), (IV) or (V):

[In the above-mentioned general formula (III) to (V), R, R¹, and R² eachrepresent a substituent, and A¹ to A³ each represent a single bond or adivalent linking group. However, the general formula (IV) excludes acase where A¹ and A² are both single bonds.]

The polyamide compound of the present invention contains a tertiaryhydrogen-containing carboxylic acid unit. Containing such a tertiaryhydrogen-containing carboxylic acid unit as the copolymerizationcomponent thereof, the polyamide compound of the present invention canexhibit excellent oxygen absorption performance even though notcontaining a transition metal, and can have good transparency.

In the present invention, the mechanism that the polyamide compoundhaving a tertiary hydrogen-containing carboxylic acid unit could realizegood oxygen absorption performance would be, though not clarified asyet, considered as follows: In the compound capable of constituting atertiary hydrogen-containing carboxylic acid unit, anelectron-attracting group and an electron-donating group bond to one andthe same carbon atom, and therefore, owing to the phenomenon that iscalled a captodative effect of energically stabilizing the unpairedelectrons existing on that carbon atoms, an extremely stable radicalcould be formed. Specifically, a carboxyl group is anelectron-attracting group, and since the carbon atom adjacent to thegroup, to which a tertiary hydrogen atom bonds, is an electron-poor (δ⁺)one, the tertiary hydrogen atom also becomes an electron-poor (δ⁺) one,therefore forming a radical as dissociated as a proton. In case whereoxygen and water exist in this state, oxygen could react with theradical and therefore the compound could exhibit oxygen absorptionperformance. In this connection, it has been known that in anenvironment having a higher humidity and a higher temperature, thereactivity is higher.

In the above-mentioned general formulae (III) to (V), R, R¹ and R² eachrepresent a substituent. The substituent represented by R, R¹ and R² inthe present invention includes a halogen atom (e.g., a chlorine atom, abromine atom, an iodine atom), an alkyl group (a linear, branched orcyclic alkyl group having from 1 to 15, preferably from 1 to 6 carbonatoms, for example, a methyl group, an ethyl group, an n-propyl group,an isopropyl group, a t-butyl group, an n-octyl group, a 2-ethylhexylgroup, a cyclopropyl group, a cyclopentyl group), an alkenyl group (alinear, branched or cyclic alkenyl group having from 2 to 10, preferablyfrom 2 to 6 carbon atoms, for example, a vinyl group, an allyl group),an alkynyl group (an alkynyl group having from 2 to 10, preferably from2 to 6 carbon atoms, for example, an ethynyl group, a propargyl group),an aryl group (an aryl group having from 6 to 16, preferably from 6 to10 carbon atoms, for example, a phenyl group, a naphthyl group), aheterocyclic group (a monovalent group having from 1 to 12, preferablyfrom 2 to 6 carbon atoms, as derived from a 5-membered or 6-membered,aromatic or non-aromatic heterocyclic compound by removing one hydrogenatom therefrom, for example, a 1-pyrazolyl group, a 1-imidazolyl group,a 2-furyl group), a cyano group, a hydroxyl group, a nitro group, analkoxy group (a linear, branched or cyclic alkoxy group having from 1 to10, preferably from 1 to 6 carbon atoms, for example, a methoxy group,an ethoxy group), an aryloxy group (an aryloxy group having from 6 to12, preferably from 6 to 8 carbon atoms, for example, a phenoxy group),an acyl group (a formyl group, an alkylcarbonyl group having from 2 to10, preferably from 2 to 6 carbon atoms, or an arylcarbonyl group havingfrom 7 to 12, preferably from 7 to 9 carbon atoms, for example, anacetyl group, a pivaloyl group, a benzoyl group), an amino group (anamino group, an alkylamino group having from 1 to 10, preferably from 1to 6 carbon atoms, an anilino group having from 6 to 12, preferably from6 to 8 carbon atoms, or a heterocyclic amino group having from 1 to 12,preferably from 2 to 6 carbon atoms, for example, an amino group, amethylamino group, an anilino group), a mercapto group, an alkylthiogroup (an alkylthio group having from 1 to 10, preferably from 1 to 6carbon atoms, for example, a methylthio group, an ethylthio group), anarylthio group (an arylthio group having from 6 to 12, preferably from 6to 8 carbon atoms, for example, a phenylthio group), a heterocyclic thiogroup (a heterocyclic thio group having from 2 to 10, preferably from 1to 6 carbon atoms, for example, a 2-benzothiazolylthio group), an imidogroup (an imido group having from 2 to 10, preferably from 4 to 8 carbonatoms, for example, an N-succinimido group, an N-phthalimido group),etc.

Of the functional groups, those having a hydrogen atom may be furthersubstituted with the above-mentioned group. For example, there arementioned an alkyl group substituted with a hydroxyl group (e.g., ahydroxyethyl group), an alkyl group substituted with an alkoxy group(e.g., a methoxyethyl group), an alkyl group substituted with an arylgroup (e.g., a benzyl group), an aryl group substituted with an alkylgroup (e.g., a p-tolyl group), an aryloxy group substituted with analkyl group (e.g., a 2-methylphenoxy group), etc., to which, however,the present invention is not limited.

In case where the functional group is further substituted, theabove-mentioned carbon number does not include the carbon number of theadditional substituent. For example, a benzyl group is considered as analkyl group having 1 carbon atom and substituted with a phenyl group,but is not considered as an alkyl group substituted with a phenyl groupand having 7 carbon atoms. Unless otherwise specifically indicated, thesame shall apply to the carbon number referred to hereinunder.

In the general formulae (VI) and (V), A¹ to A³ each represent a singlebond or a divalent linking group. However, the general formula (IV)excludes a case where A¹ and A² are both single bonds. The divalentlinking group includes, for example, a linear, branched or cyclicalkylene group (an alkylene group having from 1 to 12, preferably from 1to 4 carbon atoms, for example, a methylene group, an ethylene group),an aralkylene group (an aralkylene group having from 7 to 30, preferablyfrom 7 to 13 carbon atoms, for example, a benzylidene group), an arylenegroup (an arylene group having from 6 to 30, preferably from 6 to 15carbon atoms, for example, a phenylene group), etc. These may furtherhave a substituent. The substituent may include the functional groupsexemplified hereinabove for the substituents represented by R, R¹ andR². For example, there are mentioned an arylene group substituted withan alkyl group (for example, a xylylene group), etc., to which, however,the present invention is not limited.

Preferably, the polyamide resin of the present invention contains atleast one of the constituent units represented by any of theabove-mentioned general formulae (III) to (V). Of those, more preferredis a carboxylic acid unit having a tertiary hydrogen atom at the acarbon atom (carbon atom adjacent to the carboxyl group), from theviewpoint of the availability of the starting material and of theadvanced oxygen absorbability of the compound; and more preferred is theconstituent unit represented by the general formula (III).

R in the general formula (III) is as mentioned above. Above all, morepreferred are a substituted or unsubstituted alkyl group and asubstituted or unsubstituted aryl group; even more preferred are asubstituted or unsubstituted alkyl group having from 1 to 6 carbonatoms, and a substituted or unsubstituted aryl group having from 6 to 10carbon atoms; and still more preferred are a substituted orunsubstituted alkyl group having from 1 to 4 carbon atoms, and asubstituted or unsubstituted phenyl group.

Preferred examples of R include a methyl group, an ethyl group, ann-propyl group, an isopropyl group, an n-butyl group, a t-butyl group, a1-methylpropyl group, a 2-methylpropyl group, a hydroxymethyl group, a1-hydroxyethyl group, a mercaptomethyl group, a methylsulfanylethylgroup, a phenyl group, a naphthyl group, a benzyl group, a4-hydroxybenzyl group, etc., to which, however, the present invention isnot limited. Of those, more preferred are a methyl group, an ethylgroup, a 2-methylpropyl group and a benzyl group.

The compound capable of constituting the constituent unit represented bythe general formula (III) includes α-amino acids such as alanine,2-aminobutyric acid, valine, norvaline, leucine, norleucine,tert-leucine, isoleucine, serine, threonine, cysteine, methionine,2-phenylglycine, phenylalanine, tyrosine, histidine, tryptophane,proline, etc., to which, however, the present invention is not limited.

The compound capable of constituting the constituent unit represented bythe general formula (IV) includes O-amino acids such as 3-aminobutyricacid, etc.; and the compound capable of constituting the constituentunit represented by the general formula (V) includes dicarboxylic acidssuch as methylmalonic acid, methylsuccinic acid, malic acid, tartaricacid, etc., to which, however, the invention is not limited.

These may be any of a D-form, an L-form or a racemic form, and may alsobe an allo-form. One alone or two or more of these may be used hereeither singly or as combined.

Of those, especially preferred is an α-amino acid having a tertiaryhydrogen atom at the a carbon atom, from the viewpoint of theavailability of the starting material and of the advanced oxygenabsorbability of the compound. Of the α-amino acid, most preferred isalanine from the viewpoint of the availability, the low cost and thepolymerizability thereof and of the low yellow index (Y1) of thepolymer. Alanine has a relatively low molecular weight, and thecopolymerization ratio thereof per gram of the polyamide compound of thepresent invention is therefore high, and accordingly, the oxygenabsorption performance per gram of the polyamide compound with alanineis good.

The purity of the compound capable of constituting the tertiaryhydrogen-containing carboxylic acid unit is preferably at least 95%,from the viewpoint of the influence thereof on the polymerization suchas delay in polymerization rate thereof as well as on the quality suchas the yellow index of the polymer, more preferably at least 98.5%, evenmore preferably at least 99%. The amount of sulfate ion and ammonium ionto be contained in the compound as impurities therein is preferably atmost 500 ppm, more preferably at most 200 ppm, even more preferably atmost 50 ppm.

1-4. ω-Aminocarboxylic Acid Unit

In case where the polyamide compound of the present invention is neededto have flexibility, the polyamide compound may further contain anω-aminocarboxylic acid unit represented by the following general formula(A), in addition to the above-mentioned diamine unit, dicarboxylic acidunit and tertiary hydrogen-containing carboxylic acid unit therein.

[In the above-mentioned general formula (A), p indicates an integer offrom 2 to 18.]

The content of the ω-aminocarboxylic acid unit is preferably from 0.1 to99.7 mol in all the constituent units of the polyamide compound, morepreferably from 3 to 40 mol %, even more preferably from 5 to 35 mol %.However, the total of the diamine unit, the dicarboxylic acid unit, thetertiary hydrogen-containing carboxylic acid unit and theω-aminocarboxylic acid unit should not exceed 100 mol %.

In the general formula (A), p indicates an integer of from 2 to 18,preferably from 3 to 16, more preferably from 4 to 14, even morepreferably from 5 to 12.

The compound capable of constituting the ω-aminocarboxylic acid unitrepresented by the general formula (A) includes an ω-aminocarboxylicacid having from 5 to 19 carbon atoms, and a lactam having from 5 to 19carbon atoms. The ω-aminocarboxylic acid having from 5 to 19 carbonatoms includes 6-aminohexanoic acid, 12-aminododecanoic acid, etc.; andthe lactam having from 5 to 19 carbon atoms includes ε-caprolactam andlaurolactam, to which, however, the present invention is not limited.One alone or two or more of these may be used here either singly or ascombined.

Preferably, the ω-aminocarboxylic acid unit contains a 6-aminohexanoicacid unit and/or a 12-aminododecanoic acid unit in an amount of at least50 mol % in total in the ω-aminocarboxylic acid unit; and the content ismore preferably at least 70 mol %, even more preferably at least 80 mol%, still more preferably at least 90 mol %, and is preferably at most100 mol %.

Preferred examples of the polyamide compound of the present inventioninclude α-amino acid-copolymerized polyhexamethyleneadipamide (α-aminoacid-copolymerized N66), α-amino acid-copolymerizedpolyhexamethylenesebacamide (α-amino acid-copolymerized N610), α-aminoacid-copolymerized polyhexamethylenedodecanamide (α-aminoacid-copolymerized N612), α-amino acid-copolymerizedpolyhexamethyleneisophthalamide (α-amino acid-copolymerized N6I),α-amino acid-copolymerized polyhexamethyleneterephthalamide (α-aminoacid-copolymerized N6T), α-amino acid-copolymerized(polyhexamethyleneisophthalamide/polyhexamethyleneterephthalaimidecopolymer) (α-amino acid-copolymerized N6IT), α-amino acid-copolymerized(nylon 6/polyhexamethyleneadipamide copolymer) (α-aminoacid-copolymerized N6,66), α-amino acid-copolymerized (nylon12/polyhexamethyleneadipamide copolymer) (α-amino acid-copolymerizedN12,66), etc. In these, the α-amino acid is as mentioned above.

1-5. Degree of Polymerization of Polyamide Compound

For the degree of polymerization of the polyamide compound of thepresent invention, used is a relative viscosity thereof. The relativeviscosity of the polyamide compound of the present invention ispreferably from 1.01 to 4.2.

In case where the polyamide compound of the present invention is apolyamide resin, the relative viscosity thereof is preferably from 1.5to 4.2 from the viewpoint of the appearance of the molded productsthereof and of the forming workability thereof, more preferably from 1.7to 4.0, even more preferably from 2.0 to 3.8. However, in case where thepolyamide resin of the present invention is used as an additive, amodifier or the like for other thermoplastic resins, the range shouldnot apply thereto.

In case where the polyamide compound of the present invention is apolyamide oligomer, the relative viscosity thereof is preferably from1.01 to less than 1.5 from the viewpoint of the handleability, thereactivity and the thermal stability thereof, more preferably from 1.1to 1.49, even more preferably from 1.2 to 1.49, still more preferablyfrom 1.3 to 1.49.

The relative viscosity as referred to herein is as follows: One gram ofthe polyamide compound is dissolved in 100 mL of 96% sulfuric acid, andusing a Canon Fenske-type viscometer, the dropping time (t) thereof ismeasured at 25° C. The dropping time (t₀) of 96% sulfuric acid is alsomeasured in the same manner, and the relative viscosity of the compoundis represented by the following ratio.Relative Viscosity=t/t ₀1-6. Terminal Amino Group Concentration

The oxygen absorption rate of the polyamide compound and the oxidativedeterioration of the polyamide compound owing to oxygen absorption canbe controlled by changing the terminal amino group concentration of thepolyamide compound. In case where the polyamide compound is a polyamideresin, the terminal amino group concentration thereof is preferably from5 to 150 eq/10⁶ g from the viewpoint of the balance between the oxygenabsorption rate and the oxidative deterioration thereof, more preferablyfrom 10 to 100 eq/10⁶ g, even more preferably from 15 to 80 eq/10⁶ g.

2. Production Method for Polyamide Compound

The polyamide compound of the present invention can be produced throughpolycondensation of a diamine component capable of constituting theabove-mentioned diamine unit, a dicarboxylic acid component capable ofconstituting the above-mentioned dicarboxylic acid unit, a tertiaryhydrogen-containing carboxylic acid component capable of constitutingthe above-mentioned tertiary hydrogen-containing carboxylic acid unit,and optionally an ω-aminocarboxylic acid component capable ofconstituting the above-mentioned ω-aminocarboxylic acid unit, in whichthe degree of polymerization can be controlled by controlling thepolycondensation condition. A small amount of a monoamine or amonocarboxylic acid, serving as a molecular weight regulating agent, maybe added to the system during polycondensation. In order to control thepolycondensation reaction and to make the produced polymer have adesired degree of polymerization, the ratio (by mol) of the diaminecomponent to the carboxylic acid component to constitute the polyamidecompound may be deviated from 1.

The polycondensation method for the polyamide compound of the presentinvention includes a reactive extrusion method, a pressurized saltmethod, a normal-pressure dropwise addition method, a pressurizeddropwise addition method, etc., to which, however, the invention is notlimited. Preferably, the reaction temperature is as low as possible,since the polyamide compound can be prevented from yellowing or gellingand can have stable properties.

2-1. Reactive Extrusion Method

The reactive extrusion method is a method of reacting a polyamidecomprising a diamine component and a dicarboxylic acid component (apolyamide corresponding to the precursor of the polyamide compound ofthe present invention) or a polyamide comprising a diamine component, adicarboxylic acid component and an ω-aminocarboxylic acid component (apolyamide corresponding to the precursor of the polyamide compound ofthe present invention) with a tertiary hydrogen-containing carboxylicacid component by melt-kneading them in an extruder. This is a method ofincorporating the tertiary hydrogen-containing carboxylic acid componentinto the skeleton of the polyamide through interamidation reaction.Preferably, a screw suitable to reactive extrusion is used and adouble-screw extruder having a large L/D is used for fully attaining thereaction. This method is simple and is favorable for producing apolyamide compound that contains a small amount of a tertiaryhydrogen-containing carboxylic acid component.

2-2. Pressurized Salt Method

The pressurized salt method is a method of melt polycondensation underpressure, starting from a nylon salt as the starting material.Concretely, an aqueous solution of a nylon salt comprising a diaminecomponent, a dicarboxylic acid component, a tertiary hydrogen-containingcarboxylic acid component and optionally an ω-aminocarboxylic acidcomponent is prepared, and thereafter the aqueous solution isconcentrated and heated under pressure for polycondensation withremoving the condensation water. Inside the reactor, while the pressureis gradually restored to normal pressure, the system is heated up toaround a temperature of (melting point+10° C.) of the polyamide compoundand kept as such, and thereafter the inner pressure is gradually reducedto −0.02 MPaG and kept as such at the temperature to continue thepolycondensation. After the system has reached a predetermined stirringtorque, the reactor is pressurized with nitrogen up to 0.3 MPaG or soand the polyamide compound is then collected.

The pressurized salt method is useful in a case where a volatilecomponent is used as the monomer, and is a preferred polycondensationmethod for the case where the copolymerization ratio of the tertiaryhydrogen-containing carboxylic acid component is high. In particular,the method is favorable for the case where the tertiaryhydrogen-containing carboxylic acid component accounts for at least 15mol % of all the components constituting the polyamide compound.According to the pressurized salt method, the tertiaryhydrogen-containing carboxylic acid component can be prevented fromevaporating away, and further, polycondensation of the tertiaryhydrogen-containing carboxylic acid component alone can be prevented,and accordingly, the polycondensation reaction can be carried outsmoothly and the polyamide compound produced can have excellentproperties.

2-3. Normal-Pressure Instillation Method

The normal-pressure instillation method is a method where a diaminecomponent is continuously added dropwise to a mixture prepared byheating and melting a dicarboxylic acid component, a tertiaryhydrogen-containing carboxylic acid component and optionally anω-aminocarboxylic acid component, under normal pressure forpolycondensation with removing the condensation water. During thepolycondensation reaction, the reaction system is heated in order thatthe reaction temperature is not lower than the melting point of thepolyamide compound to be produced.

In the normal-pressure instillation method, the yield per batch is largeas compared with that in the above-mentioned pressurized salt method,since the method does not require water for salt dissolution, and inaddition, since the method does not require vaporization andcondensation of the starting material components, the reaction speedlowers little and the process time can be shortened.

2-4. Pressurized Instillation Method

In the pressurized instillation method, first a dicarboxylic acidcomponent, a tertiary hydrogen-containing carboxylic acid component andoptionally an ω-aminocarboxylic acid component are put into apolycondensation reactor, and then the components are stirred and mixedin melt to prepare a mixture. Next, while the reactor is pressurizedpreferably up to from 0.3 to 0.4 MPaG or so, a diamine component iscontinuously added dropwise to the mixture for polycondensation withremoving the condensation water. During the polycondensation reaction,the reaction system is heated in order that the reaction temperature isnot lower than the melting point of the polyamide compound to beproduced. After the components have reached a predetermined molar ratio,the addition of the diamine component is finished. While the reactor isgradually restored to normal pressure, the system therein is heated upto around a temperature of (melting point+10° C.) of the polyamidecompound to be produced, and kept as such. Subsequently, while thereactor is gradually depressurized to −0.02 MPaG, the system therein iskept as such at the temperature to continue the polycondensation. Afterthe system has reached a predetermined stirring torque, the reactor ispressurized with nitrogen up to 0.3 MPaG or so and the polyamidecompound is then collected.

Like the pressurized salt method, the pressurized instillation method isuseful in a case where a volatile component is used as the monomer, andis a preferred polycondensation method for the case where thecopolymerization ratio of the tertiary hydrogen-containing carboxylicacid component is high. In particular, the method is favorable for thecase where the tertiary hydrogen-containing carboxylic acid componentaccounts for at least 15 mol % of all the components constituting thepolyamide compound. According to the pressurized instillation method,the tertiary hydrogen-containing carboxylic acid component can beprevented from evaporating away, and further, polycondensation of thetertiary hydrogen-containing carboxylic acid component alone can beprevented, and accordingly, the polycondensation reaction can be carriedout smoothly and the polyamide compound produced can have excellentproperties. Further, different from the pressurized salt method, thepressurized instillation method does not require water for saltdissolution and therefore the yield per batch according to the method islarge. In addition, in the method, the reaction time can be shortenedand therefore the system can be prevented from gelling, like in thenormal-pressure instillation method. Accordingly, the method produces apolyamide compound having a low yellow index.

2-5. Step of Increasing Degree of Polymerization

The polyamide compound produced according to the above-mentionedpolycondensation method can be used directly as it is, however, thecompound may be processed in a step of further increasing the degree ofpolymerization thereof. The step of increasing the degree ofpolymerization includes reactive extrusion in an extruder, solid-phasepolymerization, etc. As the heating apparatus for use for solid-phasepolymerization, preferred are a continuous heating and drying apparatus;a rotary drum-type heating apparatus such as a tumble drier, a conicaldrier, a rotary drier, etc.; and a conical heating apparatus equippedwith a rotary blade inside it, such as a Nauta mixer, etc. Not limitedto these, any ordinary method and apparatus are usable in the presentinvention. In particular, for solid-phase polymerization to give thepolyamide compound, preferred is use of a rotary drum-type heatingapparatus among the above, since the system can be airtightly sealed upand the polycondensation can be readily promoted therein in a conditionwhere oxygen to cause discoloration is eliminated.

2-6. Phosphorus Atom-Containing Compound, Alkali Metal Compound

In polycondensation to produce the polyamide compound of the presentinvention, preferred is adding a phosphorus atom-containing compoundfrom the viewpoint of promoting the amidation reaction.

The phosphorus atom-containing compound includes phosphinic acidcompounds such as dimethylphosphinic acid, phenylmethylphosphinic acid,etc.; hypophosphorous acid compounds such as hypophosphorous acid,sodium hypophosphite, potassium hypophosphite, lithium hypophosphite,magnesium hypophosphite, calcium hypophosphite, ethyl hypophosphite,etc.; phosphonic acid compounds such as phosphonic acid, sodiumphosphonate, potassium phosphonate, lithium phosphonate, magnesiumphosphonate, calcium phosphonate, phenylphosphonic acid, ethylphosphonicacid, sodium phenylphosphonate, potassium phenylphosphonate, lithiumphenylphosphonate, diethyl phenylphosphonate, sodium ethylphosphonate,potassium ethylphosphonate, etc.; phosphonous acid compounds such asphosphonous acid, sodium phosphonite, lithium phosphonite, potassiumphosphonite, magnesium phosphonite, calcium phosphonite,phenylphosphonous acid, sodium phenylphosphonite, potassiumphenylphosphonite, lithium phenylphosphonite, ethyl phenylphosphonite,etc.; phosphorous acid compounds such as phosphorous acid, sodiumhydrogen phosphite, sodium phosphite, lithium phosphite, potassiumphosphite, magnesium phosphite, calcium phosphite, triethyl phosphite,triphenyl phosphite, pyrophosphorous acid, etc.

Of those, especially preferred for use herein are metal hypophosphitessuch as sodium hypophosphite, potassium hypophosphite, lithiumhypophosphite, etc., as their effect of promoting amidation is high andtheir effect of preventing discoloration is excellent. In particular,sodium hypophosphite is preferred. However, the phosphorusatom-containing compounds usable in the present invention are notlimited to the above.

The amount of the phosphorus atom-containing compound to be added ispreferably from 0.1 to 1000 ppm in terms of the phosphorus atomconcentration in the polyamide compound, more preferably from 1 to 600ppm, even more preferably from 5 to 400 ppm. When the amount is at least0.1 ppm, the polyamide compound is hardly discolored duringpolymerization and the transparency thereof could be high. When at most1000 ppm, the polyamide compound hardly gels and, in addition, themolded products of the polyamide compound would have few fish eyes thatmay be caused by the phosphorus atom-containing compound, and thereforethe appearance thereof could be good.

Also preferably, an alkali metal compound is added to thepolycondensation system to give the polyamide compound, along with thephosphorus atom-containing compound. A sufficient amount of a phosphorusatom-containing compound must be present in the system in order toprevent the discoloration of the polyamide compound duringpolycondensation, which, however, may rather cause gelation of thepolyamide compound as the case may be. Therefore, for avoiding theproblem and additionally for controlling the amidation reaction speed,it is desirable to add an alkali metal compound to the system along withthe phosphorus atom-containing compound.

The alkali metal compound is preferably an alkali metal hydroxide, analkali metal acetate, alkali metal carbonate, alkali metal alkoxides,etc. Specific examples of the alkali metal compound usable in thepresent invention include lithium hydroxide, sodium hydroxide, potassiumhydroxide, rubidium hydroxide, cesium hydroxide, lithium acetate, sodiumacetate, potassium acetate, rubidium acetate, cesium acetate, sodiummethoxide, sodium ethoxide, sodium propoxide, sodium butoxide, potassiummethoxide, lithium methoxide, sodium carbonate, etc., to which, however,the present invention is not limited. The ratio (by mol) of thephosphorus atom-containing compound to the alkali metal compound,phosphorus atom-containing compound/alkali metal compound is preferablywithin a range of from 1.0/0.05 to 1.0/1.5, from the viewpoint ofcontrolling the polymerization speed and reducing the yellow index, morepreferably from 1.0/0.1 to 1.0/1.2, even more preferably from 1.0/0.2 to1.0/1.1.

3. Polyamide Composition

The polyamide composition of the present invention is a compositioncontaining the polyamide compound of the present invention. Thepolyamide composition of the present invention is a mixture to beobtained by adding various additives and various resins to the polyamideresin or the polyamide oligomer of the present invention followed bymixing them, and in the mixture, the polyamide resin or the polyamideoligomer may react with the additives and the resins added thereto.

3-1. Additive

Depending on the desired use and performance, additives such aslubricant, crystallization nucleating agent, whitening inhibitor,delustering agent, heat-resistant stabilizer, weather-resistantstabilizer, UV absorbent, plasticizer, flame retardant, antistaticagent, discoloration inhibitor, antioxidant, impact resistance improver,etc., may be added to the polyamide compound of the present invention togive a polyamide composition. These additives may be optionally addedthereto within a range not detracting from the advantage of the presentinvention. Further, a thermoplastic resin such as elastomer or the likemay be added to the composition for imparting thereto other variousphysical properties such as enhanced impact resistance, etc.

The polyamide compound of the present invention may be mixed with theadditives in any heretofore known method, for which, however, preferredis inexpensive dry mixing that hardly receives thermal history. Forexample, there is mentioned a method where the polyamide compound andthe above-mentioned additives are added to a tumbler and mixed thereinby rotating the tumbler. In the present invention, also employable is amethod where a viscous liquid is adhered to the polyamide compound as aspreading agent and thereafter the additives are added to and mixed withthe compound, for preventing the polyamide compound and the additivesfrom separating after mixing in dry. As the spreading agent, there arementioned surfactants, etc.; however, not limited thereto, any known oneis employable in the present invention.

3-1-1. Whitening Inhibitor

In the polyamide composition of the present invention, preferably, adiamide compound and/or a diester compound are added to the polyamidecompound for preventing the composition from whitening after hot watertreatment or after long-term aging. The diamide compound and/or thediester compound are effective for preventing whitening due to oligomerprecipitation. The diamide compound and the diester compound may be usedalone, or may be used as combined.

The diamide compound for use in the present invention is preferably adiamide compound obtained from an aliphatic dicarboxylic acid havingfrom 8 to 30 carbon atoms and a diamine having from 2 to 10 carbonatoms. An aliphatic dicarboxylic acid having at least 8 carbon atoms anda diamine having at least two carbon atoms are expected to realize thewhitening-preventing effect. On the other hand, an aliphaticdicarboxylic acid having at most 30 carbon atoms and a diamine having atmost 10 carbon atoms may give a diamide compound well and uniformlydispersible in the polyamide composition. The aliphatic dicarboxylicacid may have a side chain or a double bond, but a linear saturatedaliphatic dicarboxylic acid is preferred for use herein. One alone ortwo or more different types of such diamide compounds may be used hereeither singly or as combined.

The aliphatic dicarboxylic acid includes stearic acid (C18), eicosanoicacid (C20), behenic acid (C22), montanic acid (C28), triacontanoic acid(C30), etc. The diamine includes ethylenediamine, butylenediamine,hexanediamine, xylylenediamine, bis(aminomethyl)cyclohexane, etc.Diamide compounds to be obtained by combining these are preferred here.

Preferred is a diamide compound to be obtained from an aliphaticdicarboxylic acid having from 8 to 30 carbon atoms and a diamine mainlycomprising ethylenediamine, or a diamide compound to be obtained from analiphatic dicarboxylic acid mainly comprising montanic acid and adiamine having from 2 to 10 carbon atoms; and more preferred is adiamide compound to be obtained from an aliphatic dicarboxylic acidmainly comprising stearic acid and a diamine mainly comprisingethylenediamine.

As the diester compound for use in the present invention, preferred is adiester compound to be obtained from an aliphatic dicarboxylic acidhaving 8 to 30 carbon atoms and a diol having from 2 to 10 carbon atoms.An aliphatic dicarboxylic acid having at least 8 carbon atoms and adiamine having at least 2 carbon atoms are expected to exhibit thewhitening preventing effect. On the other hand, an aliphaticdicarboxylic acid having at most 30 carbon atoms and a diol having atmost 10 carbon atoms realize good and uniform dispersion in thepolyamide composition. The aliphatic dicarboxylic acid may have a sidechain or a double bond, but preferred here is a linear saturatedaliphatic dicarboxylic acid. One alone or two or more different types ofsuch diester compounds may be used here either singly or as combined.

The aliphatic dicarboxylic acid includes stearic acid (C18), eicosanoicacid (C20), behenic acid (C22), montanic acid (C28), triacontanoic acid(C30), etc. The diol includes ethylene glycol, propanediol, butanediol,hexanediol, xylylene glycol, cyclohexanedimethanol, etc. Diestercompounds to be obtained by combining these are preferred here.

Especially preferred is a diester compound to be obtained from analiphatic dicarboxylic acid comprising mainly montanic acid and a diolcomprising mainly ethylene glycol and/or 1,3-butanediol.

In the present invention, the amount to be added of the diamide compoundand/or the diester compound may be from 0.005 to 0.5 parts by massrelative to 100 parts by mass of the polyamide compound, preferably from0.05 to 0.5 parts by mass, more preferably from 0.12 to 0.5 parts bymass. When the compound is added in an amount of at least 0.005 parts bymass relative to 100 parts by mass of the polyamide compound and whenthe compound is combined with a crystallization nucleating agent, thenthe synergistic effect for whitening prevention is expected. When theamount of the compound is at most 0.5 parts by mass relative to 100parts by mass of the polyamide compound, then the haze value of themolded products to be obtained by forming the polyamide composition ofthe present invention can be kept low.

3-1-2. Crystallization Nucleating Agent

Preferably, a crystallization nucleating agent is added to the polyamidecomposition of the present invention from the viewpoint of improving thetransparency of the composition. The agent is effective not only forimproving the transparency but also for whitening prevention throughcrystallization after hot water treatment or after long-term aging; andby adding the crystallization nucleating agent to the polyamidecompound, the crystal size can be reduced to at most ½ of the wavelengthof visible light. When the diamide compound and/or the diester compoundis used here along with the crystallization nucleating agent, theirsynergistic effect realizes much more excellent whitening preventionthan the degree thereof expected from the whitening preventing effect ofthe individual ingredients.

Inorganic crystallization nucleating agents usable in the presentinvention are those generally used for thermoplastic resins, includingglass fillers (glass fibers, milled glass fibers, glass flakes, glassbeads, etc.), calcium silicate fillers (wollastonite, etc.), mica, talc(powdery talc, or granular talc with rosin as a binder, etc.), kaolin,potassium titanate whiskers, boron nitride, clay such as phyllosilicate,nanofillers, carbon fibers, etc. Two or more of these may be used hereas combined. Preferably, the maximum diameter of the inorganiccrystallization nucleating agent is from 0.01 to 5 μm. In particular,powdery talc having a particle size of at most 3.0 μm is preferred,powdery talc having a particle size of from 1.5 to 3.0 μm or so is morepreferred, and powdery talc having a particle size of at most 2.0 μm iseven more preferred. Granular talc prepared by adding rosin as a binderto the powdery talc is especially preferred since the dispersion statethereof in the polyamide composition is good. Organic crystallizationnucleating agents preferred for use herein are micro-level to nano-levelsize bimolecular membrane capsules containing a crystallizationnucleating agent, as well as bis(benzylidene)sorbitol-type orphosphorus-containing transparent crystallization nucleating agents,rosinamide-type gelling agents, etc. Especially preferred arebis(benzylidene) sorbitol-type crystallization nucleating agents.

The amount of the crystallization nucleating agent to be added ispreferably from 0.005 to 2.0 parts by mass relative to 100 parts by massof the polyamide compound, more preferably from 0.01 to 1.5 parts bymass. At least one such crystallization nucleating agent is added to thepolyamide compound along with the diamide compound and/or the diestercompound added thereto, thereby attaining the synergistic whiteningpreventing effect. Especially preferably, the inorganic crystallizationnucleating agent such as talc or the like is added in an amount of from0.05 to 1.5 parts by mass relative to 100 parts by mass of the polyamidecompound, and the organic crystallization nucleating agent such asbis(benzylidene)sorbitol-type crystallization nucleating agent or thelike is added in an amount of from 0.01 to 0.5 parts by mass relative to100 parts by mass of the polyamide compound.

The bis(benzylidene)sorbitol-type crystallization nucleating agent isselected from bis(benzylidene)sorbitol andbis(alkylbenzylidene)sorbitol, and is a condensation product (diacetalcompound) to be produced through acetalization of sorbitol andbenzaldehyde or alkyl-substituted benzaldehyde; and this can beconveniently produced according to various methods known in the art. Inthis, the alkyl may be linear or cyclic, and may be saturated orunsaturated. An ordinary production method comprises reaction of 1 molof D-sorbitol and about 2 mol of aldehyde in the presence of an acidcatalyst. The reaction temperature may vary in a broad range dependingon the properties (melting point, etc.) of the aldehyde to be used asthe starting material for the reaction. The reaction medium may be anaqueous medium or a nonaqueous medium. One preferred method forpreparing the diacetal for use in the present invention is described inU.S. Pat. No. 3,721,682. The disclosed contents are limited tobenzylidene sorbitols; however, the bis (alkylbenzylidene) sorbitol foruse in the present invention can be conveniently produced according tothe method disclosed in the reference.

Specific examples of the bis(benzylidene) sorbitol-type crystallizationnucleating agent (diacetal compounds) includebis(p-methylbenzylidene)sorbitol, bis (p-ethylbenzylidene)sorbitol,bis(n-propylbenzylidene)sorbitol, bis (p-isopropylbenzylidene)sorbitol,bis (p-isobutylbenzylidene)sorbitol,bis(2,4-dimethylbenzylidene)sorbitol,bis(3,4-dimethylbenzylidene)sorbitol,bis(2,4,5-trimethylbenzylidene)sorbitol,bis(2,4,6-trimethylbenzylidene)sorbitol,bis(4-biphenylbenzylidene)sorbitol, etc.

Examples of the alkyl-substituted benzaldehyde suitable for preparingthe bis(benzylidene)sorbitol-type crystallization nucleating agentinclude p-methylbenzaldehyde, n-porpylbenzaldehyde,p-isopropylbenzaldehyde, 2,4-dimethylbenzlaldehyde,3,4-dimethylbenzaldehyde, 2,4,5-trimethylbenzaldehyde,2,4,6-trimethylbenzaldehyde, 4-biphenylbenzaldehyde.

When the crystallization nucleating agent such as talc, mica, clay orthe like is added to the polyamide compound, then the crystallizationspeed of the compound is accelerated by at least two times that of thepolyamide compound to which the agent is not added. This would cause noproblem in injection molding use that requires a large number of moldingcycles; however, for deep-drawn cups to be formed from a stretched filmor sheet, when the crystallization speed is too high, the film or sheetcould not be stretched owing to crystallization, or may be broken or mayhave other problems of stretching unevenness, or that is, in thesecases, the formability greatly worsens. However, thebis(benzylidene)sorbitol-type crystallization nucleating agent does notaccelerate the crystallization speed of the polyamide compound even whenadded to the compound, and therefore, the agent is preferably used fordeep-drawn caps to be formed from stretched film or sheet.

Further, it has been found that the bis(benzylidene)sorbitol-typecrystallization nucleating agent is effective not only for whiteningprevention but also for improving the oxygen barrier property of thepolyamide compound when added to the compound. Use of thebis(benzylidene)sorbitol-type crystallization nucleating agent thatrealizes both effects of whitening prevention and oxygen barrierproperty improvement is especially preferred here.

The polyamide composition of the present invention, to which is added aphyllosilicate, can be used as a gas arrier layer, and the compositioncan enhance not only the oxygen barrier property of molded products butalso the other barrier property to other gases such as carbon dioxide,etc.

The phyllosilicate is a 2-octahedral or 3-octahedral phyllosilicatehaving a charge density of from 0.25 to 0.6. The 2-octahedralphyllosilicate includes montmorillonite, beidellite, etc.; and the3-octahedral phyllosilicate includes hectorite, saponite, etc. Of those,preferred is montmorillonite.

The phyllosilicate is preferably one in which the layer-to-layerdistance is broadened by previously bringing the phyllosilicate intocontact with an organic swelling agent such as a polymer compound, anorganic compound or the like. As the organic swelling agent, preferredfor use herein is a quaternary ammonium salt, and more preferred is aquaternary ammonium salt having at least one alkyl or alkenyl group with12 or more carbon atoms.

Specific examples of the organic swelling agent includetrimethylalkylammonium salts such as trimethyldodecylammonium salts,trimethyltetradecylammonium salts, trimethylhexadecylammonium salts,trimethyloctadecylammonium salts, trimethyleicosylammonium salts, etc.;trimethylalkenylammonium salts such as trimethyloctadecenylammoniumsalts, trimethyloctadecadienylammonium salts, etc.;triethylalkylammonium salts such as triethyldodecylammonium salts,triethyltetradecylammonium salts, triethylhexadecylammonium salts,triethyloctadecylammonium salts, etc.; tributylalkylammonium salts suchas tributyldodecylammonium salts, tributyltetradecylammonium salts,tributylhexadecylammonium salts, tributyloctadecylammonium salts, etc.;dimethyldialkylammonium salts such as dimethyldidodecylammonium salts,dimethylditetradecylammonium salts, dimethyldihexadecylammonium salts,dimethyldioctadecylammonium salts, dimethylditallowammonium salts, etc.;dimethyldialkenylammonium salts such as dimethyldioctadecenylammoniumsalts, dimethyldioctadecadienylammonium salts, etc.;diethyldialkylammonium salts such as diethyldidodecylammonium salts,diethylditetradecylammonium salts, diethyldihexadecylammonium salts,diethyldioctadecylammonium salts, etc.; dibutyldialkylammonium saltssuch as dibutyldidodecylammonium salts, dibutylditetradecylammoniumsalts, dibutyldihexadecylammonium salts, dibutyldioctadecylammoniumsalts, etc.; methylbenzyldialkylammonium salts such asmethylbenzyldihexadecylammonium salts, etc.; dibenzyldialkylammoniumsalts such as dibenzyldihexadecylammonium salts, etc.;trialkylmethylammonium salts such as tridecylmethylammonium salts,tritetradecylmethylammonium salts, trioctadecylmethylammonium salts,etc.; trialkylethylammonium salts such as tridodecylethylammonium salts,etc.; trialkylbutylammonium salts such as tridodecylbutylammonium salts,etc.; ω-amino acids such as 4-amino-n-butyric acid, 6-amino-n-caproicacid, 8-aminocaprylic acid, 10-aminodecanoic acid, 12-aminododecanoicacid, 14-aminotetradecanoic acid, 16-aminohexadecanoic acid,18-aminooctadecanoic acid, etc. In addition, also usable here as anorganic swelling agent are ammonium salts containing a hydroxyl groupand/or an ether group, above all, quaternary ammonium salts containingat least one alkylene glycol residue are also usable here, such asmethyldialkyl(PAG)ammonium salts, ethyldialkyl(PAG)ammonium salts,butyldialkyl(PAG)ammonium salts, dimethylbis(PAG)ammonium salts,diethylbis (PAG) ammonium salts, dibutylbis (PAG) ammonium salts,methylalkylbis(PAG)ammonium salts, ethylalkylbis(PAG)ammonium salts,butylalkylbis(PAG)ammonium salts, methyltri(PAG)ammonium salts,ethyltri(PAG)ammonium salts, butyltri(PAG)ammonium salts, tetra (PAG)ammonium salts (in which alkyl means an alkyl group having at least 12carbon atoms such as dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl,etc.; and PAG means a polyalkylene glycol residue, preferably apolyethylene glycol residue or a polypropylene glycol residue having atmost carbon atoms). Above all, preferred are trimethyldodecylammoniumsalts, trimethyltetradecylammonium salts, trimethylhexadecylammoniumsalts, trimethyloctadecylammonium salts, dimethyldidodecylammoniumsalts, dimethylditetradecylammonium salts, dimethyldihexadecylammoniumsalts, dimethyldioctadecylammonium salts, dimethylditallowammoniumsalts. One alone or two or more different types of these organicswelling agents may be used here either singly or as combined.

In the present invention, preferably, the phyllosilicate salt treatedwith an organic swelling agent is added in an amount of from 0.5 to 8parts by mass relative to 100 parts by mass of the polyamide compound,more preferably from 1 to 6 parts by mass, even more preferably from 2to 5 parts by mass. When the amount of the phyllosilicate salt added isless than 0.5 parts by mass, then it is unfavorable since the effectthereof to improve the gas barrier property of the polyamide compositionis poor. On the other hand, when more than 8 parts by mass, it is alsounfavorable since the gas barrier layer would get cloudy thereforedetracting from the transparency of containers.

In the polyamide composition, preferably, the phyllosilicate salt isuniformly dispersed, not locally aggregated therein. Uniform dispersionas referred to herein means that the phyllosilicate salt are tabularlyseparated from each other, and at least 50% thereof are spaced from eachother via an interlayer distance of at least 5 nm. The interlayerdistance as referred to herein means the distance between centroids ofthe tabular particles. A larger interlayer distance means a betterdispersion condition; and the dispersion having a larger interlayerdistance could provide a better appearance such as better transparency,and could enhance more the gas barrier property for oxygen, carbondioxide and others.

3-1-3. Gelation Preventing/Fish Eyes Reducing Agent

In the polyamide composition of the present invention, preferably, atleast one carboxylate salt selected from sodium acetate, calciumacetate, magnesium acetate, calcium stearate, magnesium stearate, sodiumstearate and their derivatives is added to the polyamide compound. Thederivatives include metal 12-hydroxystearates such as calcium12-hydroxystearate, magnesium 12-hydroxystearate, sodium12-hydroxystearate, etc. Adding the carboxylate salt prevents gelationof the polyamide compound during working and forming the polyamidecomposition and reduces fish eyes in the resulting molded products,therefore enhancing the formability and workability of the composition.

The amount of the carboxylate salt to be added is preferably from 400 to10000 ppm as the concentration thereof in the polyamide composition,more preferably from 800 to 5000 ppm, even more preferably from 1000 to3000 ppm. When the amount is at least 400 μm, then the polyamidecompound can be prevented from being thermally deteriorated and can beprevented from gelling. On the other hand, when at most 10000 ppm, thenthe polyamide composition does not fail to be shaped and does notdiscolor or whiten. When a carboxylate salt of a basic substance existsin a molten polyamide compound, then the thermal degradation of thepolyamide compound could be retarded and the formation of a gel that isconsidered to be a final degraded product could be prevented. Theabove-mentioned carboxylate salts are excellent in handleability, andamong these, metal stearates are inexpensive and have an additionaleffect as a lubricant, and are therefore preferred for use herein ascapable of, more stabilizing the operation of working and forming thepolyamide composition. The morphology of the carboxylate salt is notspecifically defined. Preferably, the salt is powdery and has a smallparticle size as it is easy to uniformly disperse the salt in thepolyamide composition in dry mixing. Concretely, the particle size ispreferably at most 0.2 mm.

3-1-4. Antioxidant

Preferably, an antioxidant is added to the polyamide composition of thepresent invention from the viewpoint of controlling the oxygenabsorption performance of the composition and inhibiting the physicalproperties of the composition from worsening. Examples of theantioxidant include a copper-based antioxidant, a hindered phenol-typeantioxidant, a hindered amine-type antioxidant, a phosphorus-containingantioxidant, a thio-type antioxidant, etc. Above all, preferred are ahindered phenol-type antioxidant and a phosphorus-containingantioxidant.

Specific examples of the hindered phenol-type antioxidant includetriethylene glycol bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate,4,4′-butylidene-bis(3-methyl-6-t-butylphenol), 1,6-hexanediolbis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate,2,4-bis-(n-octylthio-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine,pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],2,2-thio-diethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate,2,2-thiobis(4-methyl-6-1-butylphenol),N,N′-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydroxycinnamide),3,5-di-t-butyl-4-hydroxy-benzylphosphonate-diethyl ester,1,3,5-trimethyl-2,4,6-tris(3,5-di-butyl-4-hydroxybenzyl)benzene, ethylcalcium bis(3,5-di-t-butyl-4-hydroxybenzyl)sulfonate,tris-(3,5-di-t-butyl-4-hydroxybenzyl)-isocyanurate,2,6-di-t-butyl-p-cresol, butylated hydroxyanisole,2,6-di-t-butyl-4-ethylphenol,stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate,2,2′-methylenebis-(4-methyl-6-t-butylphenol),2,2′-methylene-bis(4-ethyl-6-t-butylphenol),4,4′-thiobis-(3-methyl-6-t-butylphenol), octylated diphenylamine,2,4-bis[(octylthio)methyl]-O-cresol,isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate,4,4′-butylidenebis(3-methyl-6-t-butylphenol),3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydrorxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetroxaspiro[5,5]undecane,1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane,1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene,bis[3,3′-bis(4′-hydroxy-3′-t-butylphenyl)butyric acid]glycol ester,1,3,5-tris(3′,5′-di-t-butyl-4′-hydroxybenzyl)-sec-triazine-2,4,6-(1H,3H,5H)trione,d-α-tocopherol, etc. These may be used here either alone or as combined.Specific examples of commercial products of hindered phenol compoundsinclude BASF's Irganox 1010 and Irganox 1098 (both trade names).

Specific examples of the phosphorus-containing antioxidant includeorganic phosphorus compounds such as triphenyl phosphite, trioctadecylphosphite, tridecyl phosphite, trinonylphenyl phosphite,diphenylisodecyl phosphite,bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite,bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite,tris(2,4-di-tert-butylphenyl)phosphite, distearylpentaerythritoldiphosphite, tetra(tridecyl-4,4′-isopropylidenediphenyl)diphosphite,2,2-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite, etc. These maybe used here either alone or as combined.

The content of the antioxidant in the polyamide compound is not limited,falling within a range not detracting from the properties of thecomposition. However, from the viewpoint of controlling the oxygenabsorption performance of the composition and inhibiting the physicalproperties of the composition from worsening, the content is preferablyfrom 0.001 to 3 parts by mass relative to 100 parts by mass of thepolyamide compound of the present invention, more preferably from 0.01to 1 part by mass.

3-1-5. Impact Resistance Improver

An impact resistance improver may be added to the amide compositioncontaining the polyamide compound of the present invention for improvingthe impact resistance of the composition and improving the pinholeresistance and the flexibility of the films of the composition. Theimpact resistance improver to be added includes polyolefin, polyamideelastomer, hydrogenated styrene-butadiene copolymer resin, ionomer,ethylene-ethyl acrylate copolymer resin, maleic anhydride-modifiedethylene-ethyl acrylate copolymer resin, ethylene-methacrylic acidcopolymer resin, nylon 6, 66, 12, nylon 12 elastomer, ethylene-propylenecopolymer elastomer, polyester elastomer, etc. The amount of the impactresistance improver to be added is preferably from 1 to 10% by mass,more preferably from 1 to 5% by mass, even more preferably from 2 to 3%by mass. When the added amount is too large, then the transparency andthe gas barrier property of the composition may lower. When the addedamount is too small, then the impact resistance, and the pinholeresistance and the flexibility of the films of the composition could notbe enhanced so much.

3-1-6. Metal

In case where the polyamide composition of the present invention isrequired to have additional oxygen absorption performance in addition tothe oxygen absorbing effect thereof, at least one metal atom selectedfrom Group VIII transition metals of the Periodic Table, and manganese,copper and zinc may be added thereto in the form of a compound or ametal complex thereof, before the start of polycondensation reaction orduring the reaction or during extrusion.

In the present invention, when the metal atom is added to and mixed withthe polyamide composition, preferably, a compound containing the metalatom (hereinafter this may be referred to as a metal catalyst compound)is used. The metal catalyst compound may be used here in the form of alow-valence inorganic acid salt, organic acid salt or complex salt ofthe metal atom.

The inorganic acid salt includes halides such as chlorides, bromides,etc.; and sulfates, nitrates, phosphates, silicates, etc. On the otherhand, the organic acid salt includes carboxylate salts, sulfonate salts,phosphonate salts, etc. Also usable here are transition metal complexeswith a β-diketone or β-keto acid ester, etc. Above all, especiallypreferred are carboxylates, halides and acetylacetonate complexescontaining the above-mentioned metal atom, as their oxygen absorptionfunction is good.

One or more different types of the above-mentioned metal catalystcompounds may be added to the composition. Especially preferred arethose containing cobalt as the metal atom, as their oxygen absorptionfunction is good.

The concentration of the metal atom to be added to the polyamidecompound is not specifically defined. Preferably, the concentration isfrom 1 to 1000 ppm relative to 100 parts by mass of the polyamidecompound, more preferably from 1 to 700 ppm. When the amount added ofthe metal atom is at least 1 ppm, then the polyamide composition of thepresent invention can sufficiently express the oxygen absorptionfunction thereof in addition to the oxygen absorption effect thereof,therefore realizing the effect of enhancing the oxygen barrier propertyof packaging materials of the composition. The method of adding themetal catalyst compound to the polyamide composition is not specificallydefined, and the compound may be added thereto in any desired method.

3-2. Resin

The polyamide compound of the present invention may be mixed withvarious resins in accordance with the intended use and performance togive a polyamide composition. Not specifically defined, the resin to bemixed with the polyamide compound of the present invention is preferablyat least one selected from a group consisting of polystyrenes,polycarbonates, polyolefins, polyesters, polyamides, polyvinyl alcoholsand vegetable-derived resins.

Of those, preferred is blending with a resin having a high oxygenbarrier performance such as polyester, polyamide and polyvinyl alcohol,for effectively exhibiting the oxygen absorbing effect.

Any conventional known method is employable for mixing the polyamidecompound with resin, but preferred is melt-mixing. In case where thepolyamide compound of the present invention is melt-mixed with a resinand formed into desired pellets or molded products, they may bemelt-blended with an extruder or the like. The extruder may be asingle-screw or double-screw extruder, but from the viewpoint of themixing performance thereof, preferred is a double-screw extruder. As thescrew for melting, usable here are any known screws, for example, thosefor nylon or polyolefin, as well as those for mild compression or rapidcompression, and single-flight or double-flight screws, to which,however, the present invention is not limited.

3-2-1. Polyolefin

Specific examples of the polyolefin include olefin homopolymers such aspolyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, etc.;copolymers of ethylene and α-olefin, such as ethylene-propylene randomcopolymer, ethylene-propylene block copolymer,ethylene-propylene-polybutene-1 copolymer, ethylene-cyclic olefincopolymer, etc.; other ethylene copolymers such asethylene-α,β-unsaturated carboxylic acid copolymer,ethylene-α,β-unsaturated carboxylate copolymer, ion-crosslinkedethylene-α,β-unsaturated carboxylic acid copolymer, ethylene-vinylacetate copolymer, partially or wholly-saponified ethylene-vinyl acetatecopolymer, etc.; graft-modified polyolefins produced by graft-modifyingthese polyolefins with acid anhydride such as maleic anhydride, etc.

3-2-2. Polyester

The polyester includes those formed of one or more selected frompolycarboxylic acids including dicarboxylic acids and theirester-forming derivatives, and one or more selected from polyalcoholsincluding glycol; those comprising a hydroxycarboxylic acid and itsester-forming derivative; and those comprising a cyclic ester.

The dicarboxylic acid includes saturated aliphatic dicarboxylic acidssuch as typically oxalic acid, malonic acid, succinic acid, glutaricacid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacicacid, decanedicarboxylic acid, dodecanedicarboxylic acid,tetradecanedicarboxylic acid, hexadecanedicarboxylic acid,3-cyclobutanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid,1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid,1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, dimeracid, and their ester-forming derivatives; unsaturated aliphaticdicarboxylic acids such as typically fumaric acid, maleic acid, itaconicacid, and their ester-forming derivatives; aromatic dicarboxylic acidssuch as typically orthophthalic acid, isophthalic acid, terephthalicacid, diphenic acid, 1,3-naphthalenedicarboxylic acid,1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid,2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid,4,4′-biphenyldicarboxylic acid, 4,4′-biphenylsulfonedicarboxylic acid,4,4′-biphenyletherdicarboxylic acid,1,2-bis(phenoxy)ethane-p,p′-dicarboxylic acid, pamoic acid,anthracenedicarboxylic acid, and their ester-forming derivatives; metalsulfonate group-containing aromatic dicarboxylic acids such as typically5-sodium-sulfoisophthalic acid, 2-sodium-sulfoterephthalic acid,5-lithium-sulfoisophthalic acid, 2-lithium-sulfoterephthalic acid,5-potassium-sulfoisophthalic acid, 2-potassium-sulfoterephthalic acid,and their lower alkyl ester derivatives, etc.

Of the above-mentioned dicarboxylic acids, especially preferred is useof terephthalic acid, isophthalic acid or naphthalenedicarboxylic acid,from the viewpoint of the physical properties of the polyester to beobtained, and if desired, any other dicarboxylic acid may becopolymerized with the polyester.

Other polycarboxylic acids than these dicarboxylic acids includeethanetricarboxylic acid, propanetricarboxylic acid,butanetetracarboxylic acid, pyromellitic acid, trimellitic acid,trimesic acid, 3,4,3′,4′-biphenyltetracarboxylic acid, and theirester-forming derivatives, etc.

The glycol includes aliphatic glycols such as ethylene glycol,1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol,triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol,2,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, neopentylglycol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol,1,4-cyclohexanediol, 1,2-cyclohexanedimethanol,1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol,1,4-cyclohexanediethanol, 1,10-decamethylene glycol, 1,12-docecanediol,polyethylene glycol, polytrimethylene glycol, polytetramethylene glycol,etc.; aromatic glycols such as hydroquinone, 4,4′-dihydroxybisphenol,1,4-bis(β-hydroxyethoxy)benzene, 1,4-bis(β-hydroxyethoxyphenyl)sulfone,bis(p-hydroxyphenyl)ether, bis(p-hydroxyphenyl)sulfone,bis(p-hydroxyphenyl)methane, 1,2-bis(p-hydroxyphenyl)ethane, bisphenolA, bisphenol C, 2,5-naphthalenediol, glycols prepared by adding ethyleneoxide to these glycols, etc.

Of the above-mentioned glycols, especially preferred is use of ethyleneglycol, 1,3-propylene glycol, 1,4-butylene glycol, or1,4-cyclohexanedimethanol as the main ingredient. Other polyalcoholsthan these glycols include trimethylolmethane, trimethylolethane,trimethylolpropane, pentaerythritol, glycerol, hexanetriol, etc. Thehydroxycarboxylic acid includes lactic acid, citric acid, malic acid,tartaric acid, hydroxyacetic acid, 3-hydroxyacetic acid,p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid,4-hydroxycyclohexanecarboxylic acid, and their ester-formingderivatives.

The cyclic ester includes ε-caprolactone, β-propiolactone,β-methyl-O-propiolactone, δ-valerolactone, glycolide, lactide, etc.

The ester-forming derivatives of polycarboxylic acids andhydroxycarboxylic acids include alkyl esters, acid chlorides, acidanhydrides and the like thereof.

The polyester for use in the present invention is preferably a polyesterin which the main acid component is a terephthalic acid or itsester-forming derivative or a naphthalenedicarboxylic acid or itsester-forming derivative and the main glycol component is an alkyleneglycol.

The polyester in which the main acid component is a terephthalic acid orits ester-forming derivative is preferably a polyester in which aterephthalic acid or its ester-forming derivative accounts for at least70 mol % in total of the entire acid component therein, more preferablyat least 80 mol %, even more preferably at least 90 mol %. Similarly,the polyester in which the main acid component is anaphthalenedicarboxylic acid or its ester-forming derivative ispreferably a polyester in which a naphthalenedicarboxylic acid or itsester-forming derivative accounts for at least 70 mol % in total, morepreferably at least 80 mol %, even more preferably at least 90 mol %.

The naphthalenedicarboxylic acid or its ester-forming derivative usablein the present invention is preferably 1,3-naphthalenedicarboxylic acid,1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid,2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, asexemplified hereinabove for the above-mentioned dicarboxylic acids, orthe ester-forming derivative thereof.

The polyester in which the main glycol component is an alkylene glycolis preferably a polyester in which an alkylene glycol accounts for atleast 70 mol % in total of the entire glycol component, more preferablyat least 80 mol %, even more preferably at least 90 mol %. The alkyleneglycol as referred to herein may contain a substituent or an alicyclicstructure in the molecular chain thereof.

The other copolymerization component than the above-mentionedterephthalic acid/ethylene glycol is preferably at least one selectedfrom a group consisting of isophthalic acid, 2,6-naphthalenedicarboxylicacid, diethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol,1,2-propanediol, 1,3-propanediol and 2-methyl-1,3-propanediol, from theviewpoint of satisfying both transparency and formability, and is morepreferably at least one selected from a group consisting of isophthalicacid, diethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol.

One preferred example of the polyester for use in the present inventionis a polyester in which the main recurring unit is formed of ethyleneterephthalate, and more preferred is a linear polyester containing anethylene terephthalate unit in an amount of at least 70 mol %, even morepreferred is a linear polyester containing an ethylene terephthalateunit in an amount of at least 80 mol %, and still more preferred is alinear polyester containing an ethylene terephthalate unit in an amountof at least 90 mol %.

Another preferred examples of the polyester for use in the presentinvention is a polyester in which the main recurring unit is formed ofethylene 2,6-naphthalate, and more preferred is a linear polyestercontaining an ethylene 2,6-naphthalate unit in an amount of at least 70mol %, even more preferred is a linear polyester containing an ethylene2,6-naphthalate unit in an amount of at least 80 mol %, and still morepreferred is a linear polyester containing an ethylene 2,6-naphthalateunit in an amount of at least 90 mol %.

Still another preferred example of the polyester for use in the presentinvention is a linear polyester containing a propylene terephthalateunit in an amount of at least 70 mol %, a linear polyester containing apropylene naphthalate unit in an amount of at least 70 mol %, a linearpolyester containing a 1,4-cyclohexanedimethylene terephthalate unit inan amount of at least 70 mol %, a linear polyester containing a butylenenaphthalate unit in an amount of at least 70 mol %, or a linearpolyester containing a butylene terephthalate unit in an amount of atleast 70 mol %.

As the composition of the entire polyester, preferred is a combinationof terephthalic acid/isophthalic acid//ethylene glycol, a combination ofterephthalic acid//ethylene glycol/1,4-cyclohexanedimethanol, or acombination of terephthalic acid//ethylene glycol/neopentylglycol, fromthe viewpoint of satisfying both transparency and formability.Needless-to-say, naturally, the polyester may contain a small amount (atmost 5 mol %) of diethylene glycol to be formed through dimerization ofethylene glycol during esterification (interesterification) andpolycondensation.

Still another preferred example of the polyester for use in the presentinvention is a polyglycolic acid to be obtained through polycondensationof glycolic acid or methyl glycolate or through ring-openingpolycondensation of a glycolide. The polyglycolic acid may becopolymerized with any other component such as lactide, etc.

3-2-3. Polyamide

The polyamide for use in the present invention (the “polyamide” asreferred to here indicates the polyamide resin to be mixed with the“polyamide compound” of the present invention, but does not indicate the“polyamide compound” itself of the present invention) includes apolyamide comprising, as the main constituent unit therein, a unitderived from a lactam or an aminocarboxylic acid, an aliphatic polyamidecomprising, as the main constituent unit therein, a unit derived from analiphatic diamine and an aliphatic dicarboxylic acid, a partiallyaromatic polyamide comprising, as the main constituent unit therein, aunit derived from an aliphatic diamine and an aromatic dicarboxylicacid, a partially aromatic polyamide comprising, as the main constituentunit therein, a unit derived from an aromatic diamine and an aliphaticdicarboxylic acid, etc., and if desired, the polyamide may becopolymerized with any other monomer unit than the main constituent unittherein.

The lactam or the aminocarboxylic acid for use herein includes lactamssuch as ε-caprolactam, laurolactam, etc.; aminocarboxylic acids such asaminocaproic acid, aminoundecanoic acid, etc.; aromatic aminocarboxylicacids such as para-aminomethylbenzoic acid, etc.

The aliphatic diamine for use herein includes aliphatic diamines havingfrom 2 to 12 carbon atoms, and their functional derivatives. This mayalso be an alicyclic diamine. The aliphatic diamine may be a linearchain-like aliphatic diamine or a branched chain-like aliphatic diamine.Specific examples of the linear chain-like aliphatic diamine includealiphatic diamines such as ethylene diamine, 1-methylethylenediamine,1,3-propylenediamine, tetramethylenediamine, pentamethylenediamine,hexamethylenediamine, heptamethylenediamine, octamethylenediamine,nonamethylenediamine, decamethylenediamine, undecamethylenediamine,dodecamethylenediamine, etc. Specific examples of the alicyclic diamineinclude cyclohexanediamine, 1,3-bis(aminomethyl)cyclohexane,1,4-bis(aminomethyl)cyclohexane, etc.

The aliphatic dicarboxylic acid is preferably a linear aliphaticdicarboxylic acid or an alicyclic dicarboxylic acid, more preferably alinear aliphatic dicarboxylic acid having an alkylene group with from 4to 12 carbon atoms. Examples of the linear aliphatic dicarboxylic acidof the type include adipic acid, sebacic acid, malonic acid, succinicacid, glutaric acid, pimelic acid, suberic acid, azelaic acid,undecanoic acid, undecanedioic acid, dodecanedioic, acid, dimer acid andtheir functional derivatives. The alicyclic dicarboxylic acid includesalicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid,hexahydroterephthalic acid, hexahydroisophthalic acid, etc.

The aromatic diamine includes metaxylylenediamine, paraxylylenediamine,para-bis(2-aminoethyl)benzene, etc.

The aromatic dicarboxylic acid includes terephthalic acid, isophthalicacid, phthalic acid, 2,6-naphthalenedicarboxylic acid,diphenyl-4,4′-dicarboxylic acid, diphenoxyethanedicarboxylic acid andtheir functional derivatives, etc.

Concrete polyamides include polyamide 4, polyamide 6, polyamide 10,polyamide 11, polyamide 12, polyamide 4,6, polyamide 6,6, polyamide6,10, polyamide 6T, polyamide 9T, polyamide 6IT,polymetaxylylenadipamide (polyamide MXD6), isophthalicacid-copolymerized polymetaxylylenadipamide (polyamide MXD6I),polymetaxylylenesebacamide (polyamide MXD10),polymetaxylylenedodecanamide (polyamide MXD12),poly-1,3-bisaminocyclohexaneadipamide (polyamide BAC6),polyparaxylylenesebacamide (polyamide PXD10), etc. More preferredpolyamides are polyamide 6, polyamide MXD6, polyamide MXD6I.

As the copolymerization component of the polyamide, usable is apolyether having at least one terminal amino group or at least oneterminal carboxyl group and having a number-average molecular weight offrom 2000 to 20000, or an organic carboxylic acid salt of the polyetherhaving at least one terminal amino group, or an amine salt of thepolyether having at least one carboxyl group. Concrete examples of thecomponent include bis(aminopropyl)poly(ethylene oxide) (polyethyleneglycol having a number-average molecular weight of from 2000 to 20000).

The partially aromatic polyamide may contain a constituent unit derivedfrom a tribasic or more polycarboxylic acid such as trimellitic acid,pyromellitic acid or the like, within a range within which its structureis substantially linear.

The polyamide may be produced basically according to a conventionalknown, melt polycondensation method in the presence of water or meltpolycondensation method in the absence of water, or according to asolid-phase polymerization method of further processing the polyamideobtained according to the previous melt polycondensation method. Themelt polycondensation reaction may be attained in one stage or may beattained in multiple stages. The apparatus for the method may be a batchreaction apparatus, or may be a continuous reaction apparatus. The meltpolycondensation step and the solid-phase polymerization step may beattained continuously, or may be attained intermittently as separated.

3-2-4. Polyvinyl Alcohol

Specific examples of the polyvinyl alcohol include polyvinyl alcohol,ethylene-vinyl alcohol copolymer and their partially or whollysaponified products, etc. Further, their modified products may also beusable here.

3-2-5. Vegetable-Derived Resin

Not specifically defined, concrete examples of the vegetable-derivedresin include various aliphatic polyester-type biodegradable resinsstarting from any known others than petroleum, though partly overlappingwith the above-mentioned resins. The aliphatic polyester-typebiodegradable resins include, for example, poly (α-hydroxy acids) suchas polyglycolic acid (PGA), polylactic acid (PLA), etc.; polyalkylenealkanoates such as polybutylene succinate (PBS), polyethylene succinate(PES), etc.

4. Use of Polyamide Compound and Polyamide Composition

The polyamide compound and the polyamide composition of the presentinvention are usable for various applications that require oxygenbarrier property and oxygen absorption performance. For example, thepolyamide compound of the present invention can be filled in smallpouches by itself therein and can be used as an oxygen absorbent.

Typical application examples of the polyamide compound and the polyamidecomposition of the present invention include molded products ofpackaging materials, packaging containers, etc., to which, however, thepresent invention is not limited. The polyamide compound or thepolyamide composition of the present invention may be worked to give amolded product that comprises it as at least a part of the moldedproduct for use in the present invention. For example, the polyamidecompound or the polyamide composition of the present invention may beused as at least a part of a filmy or sheet-like packaging material. Inaddition, it may be used as at least a part of packaging containers suchas bottles, trays, cups, tubes, as well as various types of pouches suchas flat pouches, standing pouches, etc. The structure of the moldedproduct of the packaging material or the packaging container may be asingle-layer structure comprising a layer of the polyamide compound orthe polyamide composition of the present invention, or may be amultilayer structure comprising a combination of that layer and a layerof any other thermoplastic resin. Not specifically defined, thethickness of the layer of the polyamide compound or the polyamidecomposition of the present invention is preferably at least 1 μm.

The method for producing the molded products of packaging materials andpackaging containers is not specifically defined, for which any methodis employable. For example, for forming a filmy or sheet-like packagingmaterial, or a tubular packaging material, the polyamide compound or thepolyamide composition that has been melted through a T-die, a circulardie or the like may be extruded out through the accompanying extruder.The filmy molded product obtained according to the above-mentionedmethod may be stretched to give a stretched film. The bottle-shapedpackaging containers may be produced by injecting a molten polyamidecompound or polyamide composition into a mold from an injection-moldingmachine to prepare a preform, followed by blow-stretching it by heatingup to the stretching temperature thereof.

Containers such as trays, cups and the like can be produced according toa method of injecting a molten polyamide compound or polyamidecomposition into a mold from an injection-molding machine followed bymolding it therein, or according to a method of forming a sheet-likepackaging material in a mode of vacuum forming, pressure forming or thelike. The packaging materials and the packaging containers can beproduced according to various methods, not limited to theabove-mentioned production methods.

The packaging materials and the packaging containers obtained by the useof the polyamide compound and the polyamide composition of the presentinvention are suitable for housing and storing various goods. Forexample, they can be used for housing and storing various goods such asdrinks, seasonings, cereals, liquid and solid processed foods that areneeded to be filled in a germ-free condition or to be thermallysterilized, chemicals, liquid livingware, drugs, semiconductorintegrated circuits, electronic devices, etc.

EXAMPLES Melt Polymerization for Polyamide Compound According toPressurized Salt Method Example 1

174.2 g (1.05 mol) of hexamethylenediamine (HMDA, by Showa Chemical),174.4 g (1.05 mol) of high-purity isophthalic acid (PIA, by AGInternational Chemical), 74.8 g (0.45 mol) of high-purity terephthalicacid (PTA, by Mitsubishi Gas Chemical), 14.8 g (0.17 mol) of DL-alanine(by Musashino Chemical Laboratory) as a type of α-amino acid, and 200 gof pure water were put into a 1000-ml pressure-resistant andheat-resistant autoclave equipped with a stirring paddle (by TaiatsuTechno Corporation), and with stirring, the inside of the autoclave washeated up to 300° C. under 2.2 MPa, and kept as such for 240 minutes.Subsequently, the polymer was taken out, ground with a grinder, anddried in vacuum at 140° C. for hours thereby giving aDL-alanine-copolymerized(polyhexamethyleneisophthalamide/polyhexamethyleneterephth alamidecopolymer) (polyamide compound 1). Thepolyhexamethyleneisophthalamide/polyhexamethyleneterephtha lamidecopolymer is hereinafter referred to as “N6IT”.

Using a ¹H-NMR apparatus (400 MHz; JEOL's trade name, JNM-AL400;operation mode, NON (¹H)), the obtained polyamide compound 1 wasquantitatively analyzed for the constituent composition thereof.Concretely, using formic acid-d as a solvent, a solution of 5% by massof the polyamide compound 1 was prepared and analyzed through ¹H-NMR.

The ¹H-NMR chart of the DL-alanine-copolymerized N6IT (polyamidecompound 1) is shown in FIG. 1; and a partly enlarged view of FIG. 1 isshown in FIG. 2. The ¹H-NMR chart of N6IT (polyamide compound 17 ofComparative Example 1 given below) is shown in FIG. 3.

In FIG. 1, the absorption peaks at around 1.2 to 1.8 ppm are theabsorption peak “a” derived from the hydrogen of the methylene group notadjacent to the amide bond in hexamethylenediamine and the absorptionpeak “b” derived from the hydrogen of the methyl group in DL-alanine,which appear while overlapping with each other. The absorption peak ataround 3.2 to 3.5 ppm is the absorption peak “c” derived from thehydrogen of the methylene group adjacent to the amide bond inhexamethylenediamine. The absorption peak at around 7.6 to 8.3 ppm isthe absorption peak “d” derived from the hydrogen of the benzene ring inisophthalic acid or terephthalic acid.

In FIG. 2, the absorption peak “e” at around 7.7 ppm is derived from theproton at the 5-position of isophthalic acid; the absorption peak “f” ataround 8.1 ppm is derived from the proton at the 4 and 6-positions ofisophthalic acid; and the absorption peak “g” at around 8.3 ppm isderived from the proton at the 2-position of isophthalic acid.

The absorption peak at around 7.9 ppm is the absorption peak “h” derivedfrom the hydrogen of the benzene ring of terephthalic acid.

On the other hand, the absorption peak at around 1.5 to 1.8 ppm in FIG.3 is the absorption peak “i” derived from the hydrogen of the methylenegroup not adjacent to the amide bond in hexamethylenediamine. Theabsorption peak at around 3.2 to 3.5 ppm is the absorption peak “j”derived from the hydrogen of the methylene group adjacent to the amidebond of hexamethylenediamine. The absorption peak at around 7.6 to 8.3ppm is the absorption peak “k” derived from the hydrogen of the benzenering in isophthalic acid or terephthalic acid. In FIGS. 1 to 3, thenumerical value shown on the top of the absorption peaks is theintegrated intensity of the absorption peaks. However, the integratedintensity shown on the right side of the absorption peak “h” in FIG. 2is the total of the value of the absorption peak “f” and the value ofthe absorption peak “h”.

Here the 1H-NMR integrated value of the DL-alanine-copolymerized 6IT(FIG. 1) is compared with the 1H-NMR integrated value of N-6IT (FIG. 3).Consequently, the proton number derived from the aromatic ring in FIG. 1and FIG. 3 is settled as “4.0”, and the alanine amount in the polyamidecompound is calculated under the condition that the integrated values inFIG. 1 and FIG. 3 are calculated based on the same standards.

The amount of the DL-alanine unit in the polyamide compound iscalculated from the integrated intensity ratio of each peak, accordingto the following formula:Amount of DL-Alanine Unit in Polyamide Compound (mol%)={[(a+b)−i]/3}/{[(a+b)−i]/3+(c/4)+(d/4)]}×100.  [Numerical Formula 1]

The amount of the isophthalic acid unit in the polyamide compound iscalculated from the integrated intensity ratio of each peak, accordingto the following formula:Amount of Isophthalic Acid Unit in Polyamide Compound (mol%)=[d/4]/{[(a+b)−i]/3+(c/4)+(d/4)}×e/{[(h+f)/4]+e/2}×100.  [NumericalFormula 2]

The above calculation identifies the existence of DL-alanine unit in anamount of about 5.2 mol % (5.75 mol % as calculated) and isophthalicacid in an amount of 33.2 mol % (30.3 mol % as calculated) in thepolyamide compound 1. Accordingly, the molar fraction of the constituentunits in the polyamide compound 1 was identified to be HMDA unit/PIAunit/PTA unit/DL-alanine unit=47.4/33.2/14.2/5.2 mol %.

Also in the following Examples and Comparative Examples, the preparedpolyamide compounds were analyzed and quantified for the constituentcomposition thereof in the same manner as above.

Example 2

A D-alanine-copolymerized N6IT (polyamide compound 2: HMDA unit/PIAunit/PTA unit/D-alanine unit 47.4/33.2/14.2/5.2 mol %) was producedaccording to the same method as in Example 1 except that the α-aminoacid was changed to D-alanine (by Musashino Chemical Laboratory).

Example 3

An L-alanine-copolymerized N6IT (polyamide compound 3: HMDA unit/PIAunit/PTA unit/L-alanine unit 47.4/33.2/14.2/5.2 mol %) was producedaccording to the same method as in Example 1 except that the α-aminoacid was changed to L-alanine (by Sinogel Amino Acid Co., Ltd.).

Example 4

A DL-2-aminobutyric acid-copolymerized N6IT (polyamide compound 4: HMDAunit/PIA unit/PTA unit/DL-2-aminobutyric acid unit=47.4/33.2/14.2/5.2mol %) was produced according to the same method as in Example 1 exceptthat the α-amino acid was changed to DL-2-aminobutyric acid (pureproduct, by Nippon Finechem).

Example 5

A DL-leucine-copolymerized N6IT (polyamide compound 5: HMDA unit/PIAunit/PTA unit/DL-leucine unit 47.4/33.2/14.2/5.2 mol %) was producedaccording to the same method as in Example 1 except that the α-aminoacid was changed to DL-leucine (by Ningbo Haishuo Biotechnology).

Example 6

A DL-phenylalanine-copolymerized N6IT (polyamide compound 6: HMDAunit/PIA unit/PTA unit/DL-phenylalanine unit=47.4/33.2/14.2/5.2 mol %)was produced according to the same method as in Example 1 except thatthe α-amino acid was changed to DL-phenylalanine (by Sinogel Amino AcidCo., Ltd.).

Example 7

A DL-alanine-copolymerized N6IT (polyamide compound 7: HMDA unit/PIAunit/PTA unit/DL-alanine unit 49.5/34.7/14.8/1.00 mol %) was producedaccording to the same method as in Example 1 except that the amount ofDL-alanine to be added was so changed that the content thereof in thepolyamide compound could be about 1 mol %.

Example 8

A DL-alanine-copolymerized N6IT (polyamide compound 8: HMDA unit/PIAunit/PTA unit/DL-alanine unit 41.1/28.8/12.4/17.7 mol %) was producedaccording to the same method as in Example 1 except that the amount ofDL-alanine to be added was so changed that the content thereof in thepolyamide compound could be about 18 mol %.

Example 9

A DL-alanine-copolymerized N6IT (polyamide compound 9: HMDA unit/PIAunit/PTA unit/DL-alanine unit 31.0/21.7/9.30/38.0 mol %) was producedaccording to the same method as in Example 1 except that the amount ofDL-alanine to be added was so changed that the content thereof in thepolyamide compound could be about 38 mol %.

Example 10

A DL-alanine-copolymerized polyhexamethyleneisophthalamide (polyamidecompound 10: HMDA unit/PIA unit/DL-alanine unit=47.4/47.4/5.2 mol %) wasproduced according to the same method as in Example 1 except thathigh-purity terephthalic acid was not added but the amount ofhigh-purity isophthalic acid to be added was changed to 249.2 g (1.5mol). Polyhexamethyleneisophthalamide is hereinafter referred to as“N6I”.

Example 11

A DL-alanine-copolymerized polyhexamethyleneterephthalamide (polyamidecompound 11: HMDA unit/PTA unit/DL-alanine unit=47.4/47.4/5.2 mol %) wasproduced according to the same method as in Example 1 except thathigh-purity isophthalic acid was not added but the amount of high-purityterephthalic acid to be added was changed to 249.2 g (1.5 mol).Polyhexamethyleneterephthalamide is hereinafter referred to as “N6T”.

Example 12

174.2 g (1.5 mol) of hexamethylenediamine (HMDA, by Showa Chemical),219.2 g (1.5 mol) of adipic acid (by Asahi Kasei Chemicals), 14.8 g(0.17 mol) of DL-alanine (by Musashino Chemical Laboratory) as a type ofα-amino acid, and 200 g of pure water were put into a 1000-mlpressure-resistant and heat-resistant autoclave equipped with a stirringpaddle (by Taiatsu Techno Corporation), and with stirring, the inside ofthe autoclave was heated up to 280° C. under 2.2 MPa, and kept as suchfor 240 minutes. Subsequently, the polymer was taken out, ground with agrinder, and dried in vacuum at 140° C. for hours thereby giving aDL-alanine-copolymerized polyhexamethyleneadipamide (polyamide compound12: HMDA unit/adipic acid unit/DL-alanine unit=47.4/47.4/5.2 mol %).Polyhexamethyleneadipamide is hereinafter referred to as “N66”.

Example 13

174.2 g (1.5 mol) of hexamethylenediamine (HMDA, by Showa Chemical),303.4 g (1.5 mol) of sebacic acid (by Itoh Oil Chemicals), 14.8 g (0.17mol) of DL-alanine (by Musashino Chemical Laboratory) as a type ofα-amino acid, and 200 g of pure water were put into a 1000-mlpressure-resistant and heat-resistant autoclave equipped with a stirringpaddle (by Taiatsu Techno Corporation), and with stirring, the inside ofthe autoclave was heated up to 260° C. under 2.2 MPa, and kept as suchfor 240 minutes. Subsequently, the polymer was taken out, ground with agrinder, and dried in vacuum at 140° C. for hours thereby giving aDL-alanine-copolymerized polyhexamethylenesebacamide (polyamide compound13: HMDA unit/sebacic acid unit/DL-alanine unit=47.4/47.4/5.2 mol %).Polyhexamethylenesebacamide is hereinafter referred to as “N610”.

Example 14

174.2 g (1.5 mol) of hexamethylenediamine (HMDA, by Showa Chemical),345.5 g (1.5 mol) of dodecanedioic acid (by Ube Industries), 14.8 g(0.17 mol) of DL-alanine (by Musashino Chemical Laboratory) as a type ofα-amino acid, and 200 g of pure water were put into a 1000-mlpressure-resistant and heat-resistant autoclave equipped with a stirringpaddle (by Taiatsu Techno Corporation), and with stirring, the inside ofthe autoclave was heated up to 260° C. under 2.2 MPa, and kept as suchfor 240 minutes. Subsequently, the polymer was taken out, ground with agrinder, and dried in vacuum at 140° C. for hours thereby giving aDL-alanine-copolymerized polyhexamethylenedodecanamide (polyamidecompound 14: HMDA unit/dodecanedioic acid unit/DL-alanineunit=47.4/47.4/5.2 mol %). Polyhexamethylenedodecanamide is hereinafterreferred to as “N612”.

Example 15

57.4 g (0.49 mol) of hexamethylenediamine (HMDA, by Showa Chemical),72.2 g (0.49 mol) of adipic acid (by Ube Industries), 32.6 g (0.37 mol)of DL-alanine (by Musashino Chemical Laboratory) as a type of α-aminoacid, 316.8 g (2.8 mol) of ε-caprolactam (by Ube Industries), and 200 gof pure water were put into a 1000-ml pressure-resistant andheat-resistant autoclave equipped with a stirring paddle (by TaiatsuTechno Corporation), and with stirring, the inside of the autoclave washeated up to 260° C. under 2.2 MPa, and kept as such for 240 minutes.Subsequently, the polymer was taken out, ground with a grinder, anddried in vacuum at 140° C. for 8 hours thereby giving aDL-alanine-copolymerized (nylon 6/polyhexamethyleneadipamide copolymer)(polyamide compound 15: HMDA unit/adipic acid unit/DL-alanineunit/ε-caprolactam unit=11.9/11.9/8.8/67.4 mol %). Nylon6/polyhexamethyleneadipamide copolymer is hereinafter referred to as“N6,66”.

Example 16 Melt Polymerization for Polyamide Compound According toNormal-Pressure Instillation Method

A linear aliphatic dicarboxylic acid (adipic acid: 12000 g, 103.3 mol),an α-amino acid (DL-alanine: 230.1 g, 25.8 mol), sodium hypophosphite(12.9 g, 122.1 mol) and sodium acetate (7.0 g, 85.5 mol) were put into areactor having an internal volume of 50 liters and equipped with astirrer, a partial condenser, a complete condenser, a thermometer, adropping funnel, a nitrogen-introducing duct and a strand die, fullypurged with nitrogen, and then heated up to 170° C. while the system wasstirred with a small amount of nitrogen current applied thereto. HMDA(12000 g, 103.3 mol) as a type of a linear aliphatic diamine wasdropwise added thereto with stirring, and while the formed condensationwater was removed out of the system, the system was continuously heated.After the addition of the diamine, the internal temperature was kept at240° C. and the reaction was continued for 40 to 60 minutes whilespecial attention was paid to the increase in the stirring torque.Subsequently, the system was pressurized with nitrogen, and a polyamideoligomer N66 (polyamide compound 16: HMDA unit/adipic acidunit/DL-alanine unit=44.4/44.4/11.2 mol %) was taken out through thestrand die.

Comparative Example 1

1742 g (15 mol) of hexamethylenediamine (HMDA, by Showa Chemical), 1744g (10.5 mol) of high-purity isophthalic acid (PIA, by AG InternationalChemical), 748 g (4.5 mol) of high-purity terephthalic acid (PTA, byMitsubishi Gas Chemical), and 200 g of pure water were put into a10-liter pressure-resistant and heat-resistant autoclave equipped with astirring paddle (by Taiatsu Techno Corporation), and with stirring, theinside of the autoclave was heated up to 300° C. under 2.2 MPa, and keptas such for 240 minutes. Subsequently, the polymer was taken out, groundwith a grinder, and dried in vacuum at 140° C. for 8 hours therebygiving N6IT (polyamide compound 17: HMDA unit/PIA unit/PTAunit=50.0/35.0/15.0 mold).

Comparative Example 2

A glycine-copolymerized N6IT (polyamide compound 18: HMDA unit/PIAunit/PTA unit/glycine unit=47.4/33.2/14.2/5.2 mol %) was producedaccording to the same method as in Example 1 except that the α-aminoacid was changed to glycine having secondary hydrogen at the α-position(chemical reagent, by Tokyo Chemical Industry).

Comparative Example 3

A 2-aminoisobutyric acid-copolymerized N6IT (polyamide compound 19: HMDAunit/PIA unit/PTA unit/2-aminoisobutyric acid unit=47.4/33.2/14.2/5.2mol %) was produced according to the same method as in Example 1 exceptthat the α-amino acid was changed to 2-aminoisobutyric acid not havinghydrogen at the α-position (2-amino-2-methylpropanoic acid, AIB, pureproduct, by Nippon Finechem).

Comparative Example 4

N6I (polyamide compound 20) was produced according to the same method asin Example 10 except that DL-alanine was not added.

Comparative Example 5

N6T (polyamide compound 21) was produced according to the same method asin Example 11 except that DL-alanine was not added.

Comparative Example 6

N66 (polyamide compound 22) was produced according to the same method asin Example 12 except that DL-alanine was not added.

Comparative Example 7

N610 (polyamide compound 23) was produced according to the same methodas in Example 13 except that DL-alanine was not added.

Comparative Example 8

N612 (polyamide compound 24) was produced according to the same methodas in Example 14 except that DL-alanine was not added.

Comparative Example 9

N6, 66 (polyamide compound 25) was produced according to the same methodas in Example 15 except that DL-alanine was not added.

Comparative Example 10

5 parts by mass of DL-alanine (by Musashino Chemical Laboratory) wasadded to 100 parts by mass of N6IT obtained in Comparative Example 1,blended in dry, and extruded out as strands through a double-screwextruder having L/D of 37 mm (by Toshiba Machinery) at a screw rotationrate of 150 rpm, at a discharge rate of 10 kg/hr, and at an extrusiontemperature of 260° C. After cooled with water, these were cutted into apellet shape, and dried in vacuum at 140° C. for 8 hours to give apolyamide compound 26.

Comparative Example 11

N66 (polyamide compound 27) was produced according to the same method asin Example 16 except that DL-alanine was not added, the amount of sodiumhypophosphite was changed to 12.0 g (113.2 mol) and the amount of sodiumacetate was to 6.5 g (79.3 mol).

The polyamide compounds obtained in Examples and Comparative Exampleswere analyzed for the relative viscosity, the glass transitiontemperature, the melting point and the oxygen absorption thereof. Theresults are shown in Table 1.

(1) Relative Viscosity

0.2 g of the polyamide compound was accurately weighed, and dissolvedwith stirring in 100 ml of 96% sulfuric acid at 20 to 30° C. Aftercompletely dissolved, 5 ml of the solution was rapidly taken in a CanonFenske-type viscometer. This was left in a thermostat bath at 25° C. for10 minutes, and then the dropping time (t) thereof was measured. Thedropping time (t₀) of 96% sulfuric acid was also measured in the samemanner, and the relative viscosity of the sample was calculatedaccording to the following ratio.Relative Viscosity=t/t ₀(2) Glass Transition Temperature and Melting Point

Using a differential scanning calorimeter (Shimadzu's trade name,DSC-60), the sample was analyzed through DSC (differential scanningcalorimetry) in a nitrogen current atmosphere at a heating rate of 10°C./min, thereby determining the glass transition temperature (Tg) andthe melting point (Tm) thereof.

(3) Oxygen Absorption

A ground powder or pellets of the polyamide compound was formed into afilm, using a 25 mm φ single-screw extruder at an extrusion temperatureof 260° C., at a screw rotation rate of 60 rpm and at a haul-off rate of1.2 m/min, thereby giving an unstretched film sample having a width of200 mm and a thickness of about 100 μm. The film sample was cut into asize of 400 cm², and put into a three-side sealed bag of an aluminiumfoil laminate film having a size of 25 cm×18 cm, along with cottoninfiltrated with 10 ml of water therein, and sealed up so that thein-bag air amount could be 400 ml. The humidity inside the bag was madeto be 100% RH (relative humidity). After thus stored at 40° C. for 28days, the oxygen concentration inside the bag was measured with anoxygen concentration gauge (Toray Engineering's trade name, LC-700F).From the oxygen concentration, the oxygen absorption (cc/g) of thesample was calculated. The sample having a higher value of oxygenabsorption is more excellent in oxygen absorption performance and isbetter.

TABLE 1 Amino Acid Oxygen Absorption Content Relative Tg Tm (cc/g) at40° C., Polyamide Compound (mol %) Viscosity (° C.) (° C.) after 28 daysExample 1 DL-alanine-copolymerized N6IT 5.2 1.8 102 not detected 8Example 2 D-alanine-copolymerized N6IT 5.2 1.8 102 not detected 8Example 3 L-alanine-copolymerized N6IT 5.2 1.8 102 not detected 8Example 4 DL-AABA*¹⁾-copolymerized N6IT 5.2 1.5 102 not detected 8Example 5 DL-leucine-copolymerized N6IT 5.2 1.5 102 not detected 8Example 6 DL-Phe*²⁾-copolymerized N6IT 5.2 1.5 102 not detected 8Example 7 DL-alanine-copolymerized N6IT 1 1.8 102 not detected 3 Example8 DL-alanine-copolymerized N6IT 17.7 1.6 103 not detected 25 Example 9DL-alanine-copolymerized N6IT 38 1.4 105 not detected 43 Example 10DL-alanine-copolymerized N6I 5.2 1.8 122 308 8 Example 11DL-alanine-copolymerized N6T 5.2 1.8 122 308 8 Example 12DL-alanine-copolymerized N66 5.2 1.8 50 257 6 Example 13DL-alanine-copolymerized N610 5.2 1.8 41 217 7 Example 14DL-alanine-copolymerized N612 5.2 1.8 32 203 7 Example 15DL-alanine-copolymerized N6, 66 8.8 1.8 58 185 8 Example 16DL-alanine-copolymerized N66 11.2 1.6 50 248 13 Comparative N6IT 0 1.8101 243 0 Example 1 Comparative glycine-copolymerized N6IT 5.2 1.8 102not detected 0 Example 2 Comparative AIB*³⁾-copolymerized N6IT 5.2 1.8102 not detected 0 Example 3 Comparative N6I 0 1.8 122 315 0 Example 4Comparative N6T 0 1.8 122 314 0 Example 5 Comparative N66 0 1.8 50 265 0Example 6 Comparative N610 0 1.8 41 225 0 Example 7 Comparative N612 01.8 32 210 0 Example 8 Comparative N6, 66 0 1.8 58 192 0 Example 9Comparative N6IT(DL-alanine mixed)*⁴⁾ 0 1.8 101 243 0 Example 10Comparative N66 0 1.6 50 265 0 Example 11 *¹⁾DL-AABA: DL-2-aminobutyricacid *²⁾DL-Phe: DL-phenylalanine *³⁾AIB: 2-aminoisobutyric acid *⁴⁾5parts by mass DL-alanine mixed

The polyamide compound not copolymerized with an α-amino acid, thepolyamide compound copolymerized with an α-amino acid having no tertiaryhydrogen, and the polyamide compound not copolymerized with but merelymixed with a tertiary hydrogen-having α-amino acid all did not exhibitoxygen absorption performance (Comparative Examples 1 to 11).

As opposed to these, the polyamide compound copolymerized with atertiary hydrogen-having α-amino acid exhibited oxygen absorptionperformance even though not using a metal (Examples 1 to 16). Inparticular, the polyamide compounds of Examples 8 and 9 copolymerizedwith a large quantity of the α-amino acid exhibited sufficient oxygenabsorption performance.

INDUSTRIAL APPLICABILITY

The polyamide compound and the polyamide composition of the presentinvention are excellent in oxygen absorption performance. When used forpackaging materials and packaging containers, the polyamide compound orthe polyamide composition of the present invention exhibits sufficientoxygen absorption performance even though not containing a metal. Notgenerating any offensive odor, the polyamide compound or the polyamidecomposition of the present invention has extremely excellenttransparency and therefore provides packaging materials and packagingcontainers capable of storing the contents therein in a good condition.

The invention claimed is:
 1. A polyamide compound comprising: (a) 0.1 to50 mol % of a diamine unit comprising at least 50 mol % of a linearaliphatic diamine unit represented by formula (I), (b) 0.1 to 50 mol %of a dicarboxylic acid unit comprising (b1) a linear aliphaticdicarboxylic acid unit represented by formula (II-1), (b2) an aromaticdicarboxylic acid unit represented by formula (II-2), or both (b1) and(b2), wherein the dicarboxylic acid unit comprises in an amount of atleast 50 mol % in total of (b1) and (b2), and (c) 0.1 to 50 mol % of aconstituent unit represented by formula (III):

wherein in formulae (I) and (II-1), m and n each independently representan integer of 2 to 18; in formula (II-2), Ar represents an arylenegroup; in formula (III), R represents a substituted or unsubstitutedalkyl group, or a substituted or unsubstituted aryl group.
 2. Thepolyamide compound of claim 1, wherein the linear aliphatic diamine unitcomprises a hexamethylenediamine unit in an amount of at least 50 mol %.3. The polyamide compound of claim 1, wherein R in formula (III) is asubstituted or unsubstituted alkyl group having 1 to 6 carbon atoms or asubstituted or unsubstituted aryl group having 6 to 10 carbon atoms. 4.The polyamide compound of claim 1, comprising (b1) the linear aliphaticdicarboxylic acid unit, wherein the linear aliphatic dicarboxylic acidunit comprises at least one selected from the group consisting of anadipic acid unit, a sebacic acid unit and a 1,12-dodecanedicarboxylicacid unit in an amount of at least 50 mol % in total.
 5. The polyamidecompound of claim 1, comprising (b2) the aromatic dicarboxylic acidunit, wherein the aromatic dicarboxylic acid unit comprises at least oneselected from the group consisting of an isophthalic acid unit, aterephthalic acid unit and a 2,6-naphthalenedicarboxylic acid unit in anamount of at least 50 mol % in total.
 6. The polyamide compound of claim1, wherein at least one unit selected from the group consisting of thediamine unit, the dicarboxylic acid unit, and the constituent unitfurther comprise 0.1 to 99.7 mol % of an ω-aminocarboxylic acid unitrepresented by formula (A):

wherein p represents an integer of 2 to
 18. 7. The polyamide compound ofclaim 6, wherein the ω-aminocarboxylic acid unit comprises a6-aminohexanoic acid unit, a 12-aminododecanoic acid unit, or both, inan amount of at least 50 mol % in total.
 8. The polyamide compound ofclaim 1, having a relative viscosity of 1.5 to 4.2.
 9. The polyamidecompound of claim 1, having a relative viscosity of 1.01 to less than1.5.
 10. A polyamide composition comprising the polyamide compound ofclaim
 1. 11. The polyamide compound of claim 1, comprising 10 to 50 mol% of the diamine unit.
 12. The polyamide compound of claim 1, comprising10 to 50 mol % of the dicarboxylic acid unit.
 13. The polyamide compoundof claim 1, wherein an amount of the dicarboxylic acid unit is within 2mol % of an amount of the diamine unit.
 14. The polyamide compound ofclaim 1, wherein the diamine unit comprises at least 70 mol % of thelinear aliphatic diamine unit.
 15. The polyamide compound of claim 1,wherein the diamine unit comprises at least 90 mol % of the linearaliphatic diamine unit.
 16. The polyamide compound of claim 1, whereinthe dicarboxylic acid unit comprises at least 70 mol % in total of (b1)and (b2).
 17. The polyamide compound of claim 1, wherein thedicarboxylic acid unit comprises at least 90 mol % in total of (b1) and(b2).
 18. The polyamide compound of claim 1, comprising both (b1) and(b2).
 19. The polyamide compound of claim 6, wherein the diamine unit,the dicarboxylic acid unit, and the constituent unit each furthercomprise 0.1 to 99.7 mol % of the ω-aminocarboxylic acid unit.
 20. Thepolyamide compound of claim 19, wherein the diamine unit, thedicarboxylic acid unit, and the constituent unit each further comprise 5to 35 mol % of the ω-aminocarboxylic acid unit.